#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <iostream>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <ctime>

using namespace std;



/*bool cmp ( int a , int b )
{
    return (a>b);
}

int gcd ( int a , int b )
{
    return b==0 ? a : gcd ( b , a%b );
}

long long a[300006];

bool prime [10000000];

void sieve (  )
{
     prime[2]=true;
     for ( int i=4 ; i<=10000000 ; i+=2 )
     {
         prime [i]=false; prime[i-1]=true;
     }
     for ( int i=3 ; i<=3400 ; i+=2 )
     {
         if ( prime[i] )
         {
            for ( int j=i*i ; j<=10000000 ; j+=2*i )
            {
                prime[j]=false;
            }
         }
     }

}

bool p( long long x )
{
    if ( x%2==0 ) { return 0; }
    for ( int i=3 ; i*i<=x ; i+=2 )
    {
        if ( x%i==0 ) { return 0; }
    }
    return 1;

}*/

int phi( int n )
{
    double res = n;

    for ( int i=2 ; i*i<=n ; i++ )
    {
        if ( n%i==0 )
        {
            while ( n%i==0 ) { n/=i; }
            res *= ( 1.0 - ( 1.0/i ) );
        }


    }
    // if number n as a whole is prime number then the answer is n-1;
    if ( n>1 )
    {
        res *= ( 1.0 - ( 1.0/n ) );
    }


    return (int) res;



}



int main()
{

    int n;
    cin>>n;


    cout<<phi( n )<<endl;




    return 0;
}