import sys

num = input().strip()
result = set()
for i in range(len(num)):
    for j in range(i, len(num)):
        if num[i:j+1] == num[i:j+1][::-1]:
            result.add(num[i:j+1])
max_length = 0
output_word = ""
for word in result:
    if len(word) > max_length:
       max_length = len(word)
       output_word = word 
print(max_length)
# print(output_word)