def ans(ni):
    if ni[0] != '1':
        return -1
    n1 = ni[1:]
    length = len(n1)
    count_3 = n1.count('3')
    if length == 0:
        return -1
    if length != count_3:
        return -1
    return count_3


if __name__ == '__main__':
    n = list(input())
    print(ans(n))