最长回文子序列

def solve(____):
    n = len(____)
    dp = [[____] * n for _ in range(____)]
    for i in range(____):
        dp[i][i] = ____
    for length in range(____, n + ____):
        for i in range(____):
            j = i + length - ____
            if s[i] == s[j]:
                dp[i][j] = dp[i + ____][j - ____] + ____
            else:
                dp[i][j] = max(____)
    print(____)