hdu 3501 Calculation 2

#include <ctype.h>
#include <cstdio>
void read(long long &x)
{
    x=0;bool f=0;register char ch=getchar();
    for(;!isdigit(ch);ch=getchar()) if(ch==‘-‘) f=1;
    for(; isdigit(ch);ch=getchar()) x=(x<<3)+(x<<1)+ch-‘0‘;
    x=f?(~x)+1:x;
}
long long a=1,k;
long long getphi(long long n)
{
    long long ans=n;
    if(n%2==0)
    {
        while(n%2==0) n/=2;
        ans/=2;
    }
    for(int i=3;i*i<=n;i+=2)
    {
        if(n%i==0)
        {
            while(n%i==0) n/=i;
            ans=ans/i*(i-1);
        }
    }
    if(n>1) ans=ans/n*(n-1);
    return ans;
}
int main()
{
    for(;a;)
    {
        read(k);
        if(!k) break;
        long long sum=(long long)k*(k-1)/2;sum-=(long long)getphi(k)*k/2;
        printf("%lld\n",sum% 1000000007);//再忘了取模就剁手！！
    }
    return 0;
}