#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    int p, nr=0, fact=1, i=2, fact2;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    if (p==0)
        g<<1;
    else
    {


        while (nr<p)
        {
            fact = fact * i;
            fact2 = fact;
            if(fact2 % 10 == 0)
            {
                nr=0;
                while (fact2 % 10 == 0)
                {
                    nr++;
                    fact2 /= 10;
                }
            }
            i++;
        }

        g<<i-1;
    }
    return 0;
}