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

ifstream f("fact.in");
ofstream g("fact.out");
    long long p, i, j, nr, fact;
int main()
{
    f>>p;
int ok=1;
    while (ok)  {fact=1;nr=0;i++;
    for (j=1;j<=i;j++)
     fact=fact*j;
    while (fact!=0) {
        if (fact%10==0)
            nr++;
            else
                fact=0;
        fact/=10;
    }
    if (p==nr)   {
        g<<i;
        ok=0;
    }
    }
    f.close();
    g.close();
    return 0;
}