#include <fstream>
#include <cmath>
#include <limits>
using namespace std;

int verificare(int nr)
{
    int c = 0;
    int putere_cinci = 5;
    while(nr/putere_cinci > 0)
    {
        c = c + nr/putere_cinci;
        putere_cinci = putere_cinci * 5;
    }
    return c;
}

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

    int st, dr, m;
    int p;
    f>>p;

    st = 1;
    dr = p*5;
    while(st <= dr)
    {
        m = (st + dr)/2;
        if(verificare(m) < p) st = m + 1;
        else dr = m - 1;
    }
    if(verificare(st) == p) g<<st;
    else g<<-1;

    cout<<endl;
    return 0;
}