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

int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    long long  ls=200000000000, c, m,x, p, li=1;
    f>>p;
    if (p==0) g<<1;
    else
    {
        while (li<ls)
        {
            m=(li+ls)/2;
            x=m;
            c=0;
            while (x)
            {
                c=c+x/5;
                x=x/5;
            }
            if (c<p)
                li=m+1;
            else
                ls=m;
        }

    ///li==ls;
    c=0;
    while (li)
    {
        c=c+li/5;
        li=li/5;
    }
    if (c==p)
        g<<ls;
    else
        g<<-1;
}
    return 0;
}