S = input()
A = [[0 for i in range(26)] for j in range(len(S) + 1)]
for i in range(1,len(S)+1):
	c = S[i-1]
	A[i] = [n for n in A[i-1]]
	A[i][ord(c)-ord('a')] += 1

def isPal(start,end):
	l = [(A[end][i] - A[start][i]) % 2 for i in range(26)]
	odd = l.count(1)
	return odd <= 1

ans = 0
'''
s = 0
while s != len(S):
	e = len(S)
	while not isPal(s,e):
		e -= 1
	ans += 1
	s = e
'''
e = len(S)
while e != 0:
	s = 0
	while not isPal(s,e):
		s += 1
	ans += 1
	e = s
print(ans)