etf or phi in sqrt(n).cpp

#include <bits/stdc++.h>
using namespace std;
int phi(int n)
{
    int result = n;
    for (int i = 2; i * i <= n; i++)
    {
        if (n % i == 0)
        {
            while (n % i == 0)
                n /= i;
            result -= result / i;
        }
    }
    if (n > 1)
        result -= result / n;
    return result;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n;
    cin>>n;
    cout<<phi(n);
    return 0;
}