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;}