s = input()
n = len(s)
dp = [[-1]*(n+1) for _ in range(n+1)]
for l in range(n,-1,-1):
    for r in range(l+1,n+1):
        if (l != 0 or r != n) and s[l:r] == s[l:r][::-1]:
            dp[l][r] = r-l
        else:
            for x in range(l+1,r):
                if dp[l][x] >= 0 and dp[x][r] >= 0:
                    dp[l][r] = max(dp[l][r],dp[l][x],dp[x][r])
print(dp[l][r])