#include <fstream>
using namespace std;

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

int main()
{
    int k=0, p, n, putere=5;
    f >> p;
    n = 4*p;
    while(n/putere) k+=n/putere, putere*=5;
    n = 5*(n/5+1);
    do
    {
        putere=5; k=0;
        while(n/putere) k += n/putere, putere*=5;
        n+=5;
    }
    while(k<p);
    n-=5;
    if(p==0) g << 1;
    else
    {
        if(k==p) g << n;
        else g << -1;
    }
    return 0;
}