欧拉函数

#include <cstdio>
#include <iostream>
#include <queue>
#include <cmath>
using namespace std;
int n;
long long  fai(int x){
    long long re=x;
    for(int i=2;i<=sqrt(x);++i){
        if(x%i==0){
            re=re*(i-1)/i;
        }
        while(x%i==0) x/=i;
    }
    if(x!=1) re=re*(x-1)/x;
    return re;
}
int main(){
    scanf("%d",&n);
    printf("%lld",fai(n));
    return 0;
}