def solve():
    n = input()
    len_n = len(n)
    if n[0] == "1":
        return len_n - 1 if "1" + "3" * (len_n - 1) == n else -1
    if n[0] == "3":
        return len_n if "3" * len_n == n else -1
    return -1
print(solve())