【POJ1284】Primitive Roots 欧拉函数

#include<cstdio>
#include<cstring>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;

int phi(int x)
{
int xx=x,ans=x;
for(int i=2;i<=x;i++)
{
if(xx==1) break;
if(xx%i!=0) continue;
while(xx%i==0) xx/=i;
ans=ans/i*(i-1);
}
return ans;
}

int main()
{
int a;
while(scanf("%d",&a)!=EOF)
{

int ans=phi(a-1);
printf("%d\n",ans);
}
return 0;
}