HDUOJ-----2824The Euler function

The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3284    Accepted Submission(s): 1350

Problem Description

The Euler function phi is an important kind of function in number theory, (n) represents the amount of the numbers which are smaller than n and coprime to n, and this function has a lot of beautiful characteristics. Here comes a very easy question: suppose you are given a, b, try to calculate (a)+ (a+1)+....+ (b)

 

Input

There are several test cases. Each line has two integers a, b (2<a<b<3000000).

 

Output

Output the result of (a)+ (a+1)+....+ (b)

 

Sample Input

3 100

 

Sample Output

3042

 

Source

2009 Multi-University Training Contest 1 - Host by TJU

 

Recommend

 

欧拉函数....

代码：

 #include<stdio.h>
 #include<string.h>
 const int maxn=;
 __int64 phi[maxn];
 int main()
 {
     int st,en,i,j;
         for(i=;i<maxn;i++)
             phi[i]=i;
         for(i=;i<maxn;i+=)
             phi[i]/=;
         for(i=;i<maxn;i+=)
         {
             if(phi[i]==i)
             {
                 for(j=i;j<maxn;j+=i)
                 {
                     phi[j]=phi[j]/i*(i-);      /*from left to right*/
                 }
             }
         }
     while(scanf("%d%d",&st,&en)!=EOF)
     {

         __int64 ans=;
         for(i=st;i<=en;i++)
         {
             ans+=phi[i];
         }
         printf("%I64d\n",ans);
     }

     return ;
 }