sgu 102 Coprimes

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <cmath>
#define N 10010
using namespace std;

int get_phi(int n)
{
    int m = sqrt(n+0.5);
    int ans = n;
    for (int i = 2; i <= m; ++i)
        if (n % i == 0)
        {
            ans = ans / i * (i-1);
            while (n % i == 0) n /= i;
        }
    if (n > 1) ans = ans / n * (n-1);
    return ans;
}

int main()
{
    int n;
    scanf("%d", &n);
    printf("%d\n", get_phi(n));
}