#include <iostream>
#include <fstream>
#include <stdio.h>

using namespace std;

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

int main()
{
    long long p;
    f>>p;
    long long numar,i;
    numar=1;  i=1;
    long long fact;
    long long k=0;
    long long zero=1;

    //cati de zero la sfarsit
    while(k!=p)
    {
        zero=zero*10;
        k++;
    }

    while(numar%zero!=0)
    {
        numar=numar*i;
        i++;
        if(numar%zero==0)
            fact=i;
    }
    fact--;
    g<<fact;

    return 0;
}