#include <iostream>
#include <fstream>

using namespace std;

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

    int p,n=1 ;
    bool gasit = false;
    f >> p;
    int factorial=1;
    int value = 1 ;
    int contor = 0 ;


    while (gasit == false)

    {       value = 1;

        factorial = factorial * n ;
        while (factorial % 10 == 0)
        {
            value = value * 10 ;
            factorial = factorial / 10 ;
        } factorial = factorial % 10 ;


        //copie = factorial ;

        while(value !=0)
        {
            if (value % 10 == 0) { contor++; value = value / 10 ;}
            else break ;
        }

        if (contor == p) gasit = true ;
        else n++;


    }

    g<<n;

    f.close();
    g.close();


    return 0;
}