#include <bits/stdc++.h>

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

int nrz (int x)
{
    int s=0, p=5;
    while (p<=x)
    {
        s=s+x/p;
        p=p*5;
    }
    return s;
}
int main()
{
    int P, x, st, dr, ok, k, m;
    f>>P;
    st=1; dr=INT_MAX; ok=0, x=0;
    while (st<=dr && ok==0)
    {
        m=(st+dr)/2;
        k=nrz(m);
        if (k==P) {ok=1; x=m-m%5;}
        else if (k<P) st=m+1;
            else dr=m-1;
    }
    if (ok) g<<x;
    else g<<-1;
    return 0;
}