#include <fstream>
using namespace std;
  int k,p,n,pt;

int main()
{
    ifstream f("fact.in");
ofstream g("fact.out");
    f>>p;
    n = 4*p,k=0;pt=5;
    while(n/pt)
    {
        k += n/pt;
        pt*= 5;
    }
    n = 5*(n/5+1);
    do {
        pt = 5, k = 0;
        while(n/pt) k += n/pt, pt *= 5;
        n += 5;
    } while(k < p);
    n -= 5;
    if(p == 0) g<<1;
    else {
        if(k == p) g<<n;
        else g<<-1;
    }
    f.close();
    g.close();
    return 0;
}