#include <fstream>

using namespace std;

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

typedef unsigned long long ULL;
const ULL INF =-1;
int p;

int ndiv(ULL n)
{
    ULL nrd = 0;
    while (n > 0)
        nrd += n/5, n /= 5;
    return nrd;
}

ULL cb (ULL l, ULL r)
{
    ULL mid, x;

    while (l <= r)
    {
        mid = l+((r-l)/2);
        x = ndiv(mid);
        if (x < p)
            l = mid+1;
        else
            r = mid-1;
    }
    if (ndiv(l) == p)
        return l;
    g << "-1";
    return 0;
}

int main()
{
    f >> p;
    g << cb (1, INF);
    return 0;
}