#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll euler_phi(ll n) {
    ll result = n;
    for (ll 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() {
    freopen("NTCN.INP", "r", stdin);
    freopen("NTCN.OUT", "w", stdout);
    
    ll n;
    cin >> n;
    
    cout << euler_phi(n) << endl;

    return 0;
}