#include <iostream>
#include <fstream>

using namespace std;

ifstream f ("fact.in");
ofstream  g ("fact.out");

int power ( int a , int b)
{
    int i;
    int p=1;
    for(i=1;i<=b;i++)
    {
        p=p*a;
    }
    return p;

}

int Factorial ( int n)
{
    long long p=1;
    while (n>0)
    {
        p=p*n;
        n--;
    }
    return p;
}

int main()
{

    bool gasit =false;
    int p;
    f>>p;
    int i=0;
    while ( gasit==false)
    {
       i++;
       if( Factorial(i)%power(10, p )==0 ) {
               gasit=true;
       }


    }
    g<<i;
    return 0;
}