BJFU fudq的等式

 /*
  BJFU fudq的等式
  http://101.200.220.237/contest/19/problem/118/
  数论 勒让德定理 二分答案
  */
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #include <cmath>
 #include <vector>
 #include <queue>
 //#define test
 using namespace std;
 const int Nmax=;
 const long long INF=100000000000005LL;
 long long p[Nmax];
 long long times[Nmax];
 int cnt;
 long long n,x,y;

 long long Legendre(long long n,long long p,long long y)
 {
     long long ans=0LL;
     while(n>)
     {
         ans+=n/p;
         if(ans>y)
             return y+1LL;
         n/=p;
     }
     return ans;
 }

 int is(long long n)
 {
     for(int i=;i<=cnt;i++)
     {
         if(Legendre(n,p[i],times[i]*y)<times[i]*y)
             return ;
     }
     return ;
 }
 long long get()
 {
     long long n=0LL;
     long long l=1LL,r=INF;
     while(l<r)
     {
         long long mid=(l+r)>>;
         long long m=is(mid);
         //printf("l:%lld r:%lld mid:%lld x:%lld y:%lld num:%lld\n",l,r,mid,x,y,m);
         if(!m)
             l=mid+;
         else
             r=mid-;
     }
     if(n==0LL && !is(r))
         n=r+;
     else if(n==0LL && is(r))
         n=r;
     return n;

 }
 //long long get()
 //{
     //long long m=-1LL;
     //for(int i=1;i<=cnt;i++)
     //{
        //m=max(m,get(p[i],times[i]*y));
     //}
     //return m;
 //}
 int main()
 {
     #ifdef test
     #endif
     //freopen("test.in","r",stdin);
     while(scanf("%lld%lld",&x,&y)==)
     {
         cnt=;
         for(int i=;i*i<=x;i++)
         {
             if(x%i==)
             {
                 p[++cnt]=i;
                 times[cnt]=;
                 while(x%i==)
                 {
                     x/=i;
                     times[cnt]++;
                 }
             }
         }
         if(x!=)
         {
             p[++cnt]=x;
             times[cnt]=;
         }

         if(cnt==)
         {
             //printf("error\n");
             printf("0\n");
             continue;
         }
         printf("%lld\n",get());
     }
     return ;
 }