from sys import stdin

line = list(stdin.readline().strip())
if line[0] == '0':
	print(-1)
else:
	relocations = 0
	#print(line)
	while(line.count('1') != len(line)):
		zeros = [[] for _ in range(len(line))]
		shifts = [0] * len(line)
		for i, char in enumerate(line):
			if char == '0':
				for j in range(0, i):
					if line[j] == '1':
						zeros[i].append(i-j)
						shifts[i-j] += 1
		max_shift = max_i = 0
		for i, shift in enumerate(shifts):
			if shift > max_shift:
				max_shift = shift
				max_i = i
		new_line = line[:]
		for i in range(len(line) - max_i):
			if line[i] == '1':
				new_line[i + max_i] = '1'
		line = new_line
		relocations += 1
		#print(line)
	print(relocations)