#include <fstream>

using namespace std;

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

int main()
{
    int i,p,c,pt=0,put;
    f>>p;
    if (p==0)
    {
        g<<1;
        return 0;
    }
    for (i=5;pt<p;i=i+5)
    {
        put=0;
        c=i;
        while (c%5==0)
        {
            put++;
            c=c/5;
        }
        pt=pt+put;
    }
    if (pt==p)
        g<<i-5;
    else
        g<<-1;
    return 0;
}