import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N = read().rstrip()

L = len(N)
S = b'1' + b'3' * (L-1)

answer = L - 1 if N == S else -1
if answer == 0:
    answer = -1
print(answer)