HDU——T 3501 Calculation 2

http://acm.hdu.edu.cn/showproblem.php?pid=3501

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4548    Accepted Submission(s): 1878

Problem Description

Given a positive integer N, your task is to calculate the sum of the positive integers less than N which are not coprime to N. A is said to be coprime to B if A, B share no common positive divisors except 1.

 

Input

For each test case, there is a line containing a positive integer N(1 ≤ N ≤ 1000000000). A line containing a single 0 follows the last test case.

 

Output

For each test case, you should print the sum module 1000000007 in a line.

 

Sample Input

3
4
0

 

Sample Output

0
2

 

Author

GTmac

 

Source

2010 ACM-ICPC Multi-University Training Contest（7）——Host by HIT

 

欧拉函数得和==phi（n)*n/2;

md 还是见识少。。

 #include <algorithm>
 #include <cstdio>

 using namespace std;

 #define LL long long
 const LL mod();
 const LL N(+);
 LL x;

 LL phi(LL x)
 {
     LL ret=;
     for(LL i=;i*i<=x;i++)
         if(x%i==)
         {
             x/=i;
             ret*=i-;
             for(;x%i==;)
                 ret*=i,x/=i;
         }
     if(x>) ret*=x-;
     return ret;
 }

 int main()
 {
     for(;scanf("%lld",&x)&&x;)
     {
         LL zz=(x-)*x>>;
         printf("%lld\n",(zz-(x*phi(x)>>))%mod);
     }
     return ;
 }