Inversions

s = input()

b1, b2 = "0", "1"
i1, i2 = 0, 0
for c in s:
	if (c == b1):
		i1 += 1
	if (c == b2):
		i2 += 1
	b1 = "1" if b1 == "0" else "0"
	b2 = "1" if b2 == "0" else "0"
if (i1 < i2):
	print(i1)
else:
	print(i2)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED