#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
long long phi(long long n){
    long long result=n;
    for(long long p=2;p*p<=n;++p){
        if(n%p==0){
            while(n%p==0){
                n/=p;
            }
            result-=result/p;
        }
    }
    if(n>1){
        result-=result/n;
    }
    return result;
}
int32_t main()
{
    long long n;
    fin>>n;
    fout<<phi(n);

    return 0;
}