hdu 1787 GCD Again

简单的欧拉函数……

#include<iostream>
using namespace std;
typedef __int64 int64;
//const long mod=1000000007;
int64 fun(int64 n)
{
int64 ans=1;
for(int i=2;i*i<=n;i++)
{
if(n%i==0)
{
n/=i;
ans=ans*(i-1);
while(n%i==0)
{
n/=i;
ans=ans*i;
}
}
}
if(n>1)
ans*=n-1;
return ans;
}
int main()
{
int64 n,sum;
while(scanf("%I64d",&n),n)
{
sum=n-fun(n)-1;
printf("%I64d\n",sum);
}
return 0;
}