def nr_zerouri(numar):
    counter = 0
    i = 5
    while i <= numar:
        counter += numar//i
        i *= 5
    return counter

with open("fact.in", "r") as fin:
    p = int(fin.read())
    l = 1
    r = 1000000000
    ok = True
    while l <= r:
        mid = l + (r-l) // 2
        m = nr_zerouri(mid)
        if m == p:
            ans = mid
            ok = False
            r = mid-1
        elif m < p:
            l = mid+1
        else:
            r = mid-1
    with open("fact.out", "w") as fout:
        if ok:
            fout.write("-1")
        else:
            fout.write(str(ans))