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

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    int p,fact=1,gasit=0;
    f>>p;
    int i=1;
    while(gasit==0 && fact<INT_MAX)
        {
            int z=0;
            int copie=fact;
            while(copie%10==0)
            {
                    copie=copie/10;
                    z++;
            }
            if(z==p)
            {
                g<<i;
                gasit=1;
            }
            else
            {
                i++;
                fact=i*fact;
            }




        }
    return 0;
}