LCS

def LCS(A, B):
    n = len(A)
    m = len(B)

    #dp[i][j] 代表 A的前 i 个字符 与 B的前 j 个字符最长公共子序列长度
    dp = [[0] * (m + 1) for _ in range(n + 1)]

    for i in range(1, n + 1):
        for j in range(1, m + 1):
            if A[i - 1] == B[j - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
            else:
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])

    lcs_max_len = dp[n][m]

    lcs = []
    i, j = n, m

    while i > 0 and j > 0:
        if A[i - 1] == B[j - 1]:
            lcs.append(A[i - 1])
            j -= 1
            i -= 1
        elif dp[i - 1][j] > dp[i][j - 1]:
            i -= 1
        else:
            j -= 1
    lcs.reverse()

    return lcs_max_len, lcs

A = input()
B = input()
lcs_len, lcs = LCS(A, B)
print(''.join(lcs))