s = input()
n = len(s)
ok = [[False for _ in range(n)] for _ in range(n)]
for i in range(n):
    ok[i][i] = True
for i in range(n-1):
    if s[i] == s[i+1]: ok[i][i+1] = True

# print(s)
for i in range(n-2, -1, -1):
    for j in range(1, n):
        if ok[i+1][j-1] and s[i] == s[j]:
            ok[i][j] = True
# for i in range(n): print(ok[i])

dp = [0 for _ in range(n+1)]
dp[0] = 10 ** 9
for i in range(n):
    for j in range(n-i):
        if ok[i][i+j]: dp[i+j+1] = max(dp[i+j+1], min(dp[i], j+1))
# print(dp)
print(dp[n])