#include <fstream>

using namespace std;

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

    int p,n=1 ;
    f >> p;
    int factorial=1;
    int value = 1 ;



    while (n!=0)

    {       value = 1;

        factorial = factorial * n ;

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


        while(value !=0)
        {
            if (value % 10 == 0 && p !=0) { p--; value = value / 10 ;}
            else break ;
        }

        if (p == 0) {g<< n ; break ;}
        else n++;

    }

    return 0;
}