Buggy python submission (verdict: Time Limit Exceeded):
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [['' for _ in range(tt)] for __ in range(ss)]

if s[0] == t[0]:
    dp[0][0] = s[0]

for i in range(1,ss):
    if s[i] == t[0]:
        dp[i][0] = t[0]
    else:
        dp[i][0] = dp[i-1][0]

for j in range(1,tt):
    if s[0] == t[j]:
        dp[0][j] = s[0]
    else:
        dp[0][j] = dp[0][j-1]

for i in range(1, ss):
    for j in range(1, tt):
        if s[i] == t[j]:
            dp[i][j] = dp[i-1][j-1] + s[i]
            if len(dp[i][j]) < len(dp[i][j-1]):
                dp[i][j] = dp[i][j-1]
            if len(dp[i][j]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j]
        else:
            if len(dp[i][j-1]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j]
            else:
                dp[i][j] = dp[i][j-1]

print(dp[ss-1][tt-1])


Fixed submission:
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [[0 for _ in range(tt+1)] for __ in range(ss+1)]

for i in range(1, ss+1):
    for j in range(1, tt+1):
        if s[i-1] == t[j-1]:
            dp[i][j] = max(dp[i-1][j-1] + 1, dp[i][j-1], dp[i-1][j])
        else:
            dp[i][j] = max(dp[i][j-1],dp[i-1][j])

i = ss
j = tt
ans = []

while i>0 and j>0:
    if s[i-1] == t[j-1]:
        ans.append(s[i-1])
        i -= 1
        j -= 1
    else:
        if dp[i][j] == dp[i-1][j]:
            i -= 1
        else:
            j -= 1

print(''.join(reversed(ans)))

Buggy python submission (verdict: Time Limit Exceeded):
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [[[] for _ in range(tt)] for __ in range(ss)]

if s[0] == t[0]:
    dp[0][0].append(s[0])

for i in range(1,ss):
    if s[i] == t[0]:
        dp[i][0].append(t[0])
    else:
        dp[i][0] = dp[i-1][0][:]

for j in range(1,tt):
    if s[0] == t[j]:
        dp[0][j].append(s[0])
    else:
        dp[0][j] = dp[0][j-1][:]

for i in range(1, ss):
    for j in range(1, tt):
        if s[i] == t[j]:
            dp[i][j] = dp[i-1][j-1][:]
            dp[i][j].append(s[i])
            if len(dp[i][j]) < len(dp[i][j-1]):
                dp[i][j] = dp[i][j-1][:]
            if len(dp[i][j]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j][:]
        else:
            if len(dp[i][j-1]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j][:]
            else:
                dp[i][j] = dp[i][j-1][:]

print(''.join(dp[ss-1][tt-1]))


Fixed submission:
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [[0 for _ in range(tt+1)] for __ in range(ss+1)]

for i in range(1, ss+1):
    for j in range(1, tt+1):
        if s[i-1] == t[j-1]:
            dp[i][j] = max(dp[i-1][j-1] + 1, dp[i][j-1], dp[i-1][j])
        else:
            dp[i][j] = max(dp[i][j-1],dp[i-1][j])

i = ss
j = tt
ans = []

while i>0 and j>0:
    if s[i-1] == t[j-1]:
        ans.append(s[i-1])
        i -= 1
        j -= 1
    else:
        if dp[i][j] == dp[i-1][j]:
            i -= 1
        else:
            j -= 1

print(''.join(reversed(ans)))

Buggy python submission (verdict: Time Limit Exceeded):
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [['' for _ in range(tt)] for __ in range(ss)]

if s[0] == t[0]:
    dp[0][0] = s[0]

for i in range(1,ss):
    if s[i] == t[0]:
        dp[i][0] = t[0]
    else:
        dp[i][0] = dp[i-1][0]

for j in range(1,tt):
    if s[0] == t[j]:
        dp[0][j] = s[0]
    else:
        dp[0][j] = dp[0][j-1]

for i in range(1, ss):
    for j in range(1, tt):
        if s[i] == t[j]:
            dp[i][j] = dp[i-1][j-1] + s[i]
            if len(dp[i][j]) < len(dp[i][j-1]):
                dp[i][j] = dp[i][j-1]
            if len(dp[i][j]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j]
        else:
            if len(dp[i][j-1]) < len(dp[i-1][j]):
                dp[i][j] = dp[i-1][j]
            else:
                dp[i][j] = dp[i][j-1]

print(dp[ss-1][tt-1])


Fixed submission:
s = input()
t = input()

ss = len(s)
tt = len(t)

dp = [[0 for _ in range(tt+1)] for __ in range(ss+1)]

for i in range(1, ss+1):
    for j in range(1, tt+1):
        if s[i-1] == t[j-1]:
            dp[i][j] = max(dp[i-1][j-1] + 1, dp[i][j-1], dp[i-1][j])
        else:
            dp[i][j] = max(dp[i][j-1],dp[i-1][j])

i = ss
j = tt
ans = []

while i>0 and j>0:
    if s[i-1] == t[j-1]:
        ans.append(s[i-1])
        i -= 1
        j -= 1
    else:
        if dp[i][j] == dp[i-1][j]:
            i -= 1
        else:
            j -= 1

print(''.join(reversed(ans)))