#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
    long long p, n, x=0, a;
    f>>p;
    int OK=1;
    n=0;
    if (p == 0) g<<1;
       else
        while (p>=x)
        {
            n+=5;
            a=n;
            OK=1;
            while (OK==1)
                if (a%5)
                {
                    x++;
                    a/=5;
                }
                else OK=0;

            if (p==x) {g<<n; break;}

       }
       if (p<x) { g<<-1; }
    return 0;
}