uva 10820

                                                                           /* 交表 _________________________________________________________________________________

                                                                               #include <iostream>
                                                                               #include <map>
                                                                               #include <cmath>
                                                                               #include <vector>
                                                                               #include <cstdio>
                                                                               #include <string>
                                                                               #include <cstring>
                                                                               #include <algorithm>
                                                                               using namespace std;
                                                                               #define fir first
                                                                               #define sec second
                                                                               #define pb(x) push_back(x)
                                                                               #define mem(A, X) memset(A, X, sizeof A)
                                                                               #define REP(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
                                                                               #define rep(i,l,u) for(int (i)=(int)(l);(i)>=(int)(u);--(i))
                                                                               #define foreach(e,x) for(__typeof(x.begin()) e=x.begin();e!=x.end();++e)
                                                                               typedef long long LL;
                                                                               typedef unsigned long long ull;
                                                                               typedef pair<long,long>  pll;     

                                                                               LL T,n;
                                                                               const int mod=1e9+7;
                                                                               const int maxn=1e5+10;    

                                                                                         const int size=50000;//1-10000的表
                                                                                         int phi[size+1];
                                                                                         void phi_table() // 1 到 n 的欧拉phi函数值表    (  O( nlg(lgn) )  )
                                                                                         {
                                                                                             for(int i=2;i<=size;i++)
                                                                                             {
                                                                                                 phi[i]=0;
                                                                                             }
                                                                                             phi[1]=1;
                                                                                             for(int i=2;i<=size;i++)
                                                                                             {
                                                                                                 if(!phi[i])
                                                                                                 {
                                                                                                     for(int j=i;j<=size;j+=i)
                                                                                                     {
                                                                                                         if(!phi[j]) phi[j]=j;
                                                                                                         phi[j] = phi[j]/i*(i-1);
                                                                                                     }
                                                                                                 }
                                                                                             }
                                                                                         }  

                                                                            int main()
                                                                               {
                                                                                    freopen("in.txt","r",stdin);
                                                                                    phi_table();
                                                                                    while(cin>>n&&n)
                                                                                    //while(cin>>T)
                                                                                    {
                                                                                      //REP(kase,1,T)  { }
                                                                                        LL ans=1;
                                                                                        REP(i,2,n)
                                                                                        ans+=2*phi[i];
                                                                                        cout<<ans<<endl;

                                                                                    }
                                                                                 return 0;
                                                                               }

                                                                              /*
                                                                                 note    :
                                                                                 debug   :
                                                                                 optimize:
                                                                               */