#include <bits/stdc++.h>

#define ll long long
#define el cout << '\n'

using namespace std;

ll n, ans;

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen("MATH_IS_FUN.INP", "r"))
    {
        freopen("MATH_IS_FUN.INP", "r", stdin);
        freopen("MATH_IS_FUN.OUT", "w", stdout);
    }
    cin >> n;
    ans = n > 1 ? n : 0;
    for (ll i = 2; i * i <= n; i++)
    {
        bool flag = 0;
        while (n % i == 0)
        {
            n /= i;
            flag = 1;
        }
        if (flag) ans -= ans/i;
    }
    if (n > 1) ans -= ans/n;
    cout << ans;
}