HDU——T3501 Calculation 2

 1 #include <algorithm>
 2 #include <cstdio>
 3 
 4 using namespace std;
 5 
 6 #define LL long long
 7 const LL mod(1000000007);
 8 const LL N(1000000000+5);
 9 LL x;
10 
11 LL phi(LL x)
12 {
13     LL ret=1;
14     for(LL i=2;i*i<=x;i++)
15         if(x%i==0)
16         {
17             x/=i;
18             ret*=i-1;
19             for(;x%i==0;)
20                 ret*=i,x/=i;
21         }
22     if(x>1) ret*=x-1;
23     return ret;
24 }
25 
26 int main()
27 {
28     for(;scanf("%lld",&x)&&x;)
29     {
30         LL zz=(x-1)*x>>1;
31         printf("%lld\n",(zz-(x*phi(x)>>1))%mod);
32     }
33     return 0;
34 }