import std.stdio, std.string, std.conv;
import std.range, std.algorithm, std.array, std.math, std.typecons;


void main() {
    int n; scan(n);
    writeln(euler_phi(n));
}


int euler_phi(int n) {
    int ans = n;

    for (int p = 2; p*p <= n; p++) {
        if (n % p == 0) {
            ans = ans / p * (p - 1);
            while (n % p == 0) n /= p;
        }
    }

    if (n > 1) ans = ans / n * (n - 1);

    return ans;
}






void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}



void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

