查找两个字符串a,b中的最长公共子串

def solve(____):
    m, n = len(____), len(____)
    dp = [[____] * (____) for _ in range(____)]
    max_len = ____
    end_pos = ____
    for i in range(____, m + ____):
        for j in range(____, n + ____):
            if s1[i - ____] == s2[j - ____]:
                dp[i][j] = dp[i - ____][j - ____] + ____
                if dp[i][j] > max_len:
                    max_len = dp[i][j]
                    end_pos = i
    print(____)