s=eval(input())



half = len(s)//2



res = 0



for i in range(half):

    if s[i] != s[-(i+1)]:

        res += 1

print(res)
import copy



s=list(eval(input()))



s2 = copy.copy(s)



s2.reverse()



ans = 0



for i in range(len(s)//2):

    if s[i] != s2[i]:

        ans += 1

print(ans)
s = eval(input())
half = len(s) // 2
res = 0
for i in range(half):
    if s[i] != s[-(i + 1)]:
        res += 1
print(res)

import copy

s = list(eval(input()))
s2 = copy.copy(s)
s2.reverse()
ans = 0
for i in range(len(s) // 2):
    if s[i] != s2[i]:
        ans += 1
print(ans)

-s = eval(input()) -half = len(s) // 2 -res = 0 -for i in range(half): -    if s[i] != s[-(i + 1)]: -        res += 1 -print(res) +import copy + +s = list(eval(input())) +s2 = copy.copy(s) +s2.reverse() +ans = 0 +for i in range(len(s) // 2): +    if s[i] != s2[i]: +        ans += 1 +print(ans)