#include <fstream>

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

int zero(int n)
{
    if (n < 5)
        return 0;
    else
        return n/5+zero(n/5);
}
int main()
{
    int p,pas=1<<30,r=0;
    in>>p;
    if (p==0)
        out<<"1";
    else
    {
        while (pas)
        {
            if (zero(r+pas)<p)
                r+=pas;
            pas/=2;
        }
        r++;
        if (zero(r)==p)
            out<<r;
        else
            out<<-1;
    }
    return 0;
}