sgu102 Euler function

$phi[x] = x * \prod_{i = 1}^{n} (p[i]-1)/(p[i])$

#define others
#ifdef poj
#include <iostream>
#include <cstring>
#include <cmath>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <string>
#endif // poj
#ifdef others
#include <bits/stdc++.h>
#endif // others
//#define file
#define all(x) x.begin(), x.end()
using namespace std;
const double eps = 1e-8;
int dcmp(double x) { if(fabs(x)<=eps) return 0; return (x>0)?1:-1;};
typedef long long LL;


namespace solver {
    const int maxn = 300;
    int phi(int x) {
        int v = x;
        for(int i = 2; i <= sqrt(x); i++){
            if(x % i == 0) {
                v *= i - 1;
                v /= i;
                while(x % i == 0) {
                    x /= i;
                }
            }
        }
        if(x != 1) {
            v *= x-1;
            v /= x;
        }
        return v;
    }
    void solve() {
        int n;
        scanf("%d", &n);
        cout<<phi(n);
    }
}

int main() {
#ifdef file
    freopen("gangsters.in", "r", stdin);
    freopen("gangsters.out", "w", stdout);
#endif // file
//    int t;
//    scanf("%lld", &t);
//    while(t--)
    solver::solve();
    return 0;
}

/*
4
0 1
1 2
2 3
3 4
*/