Buggy python submission (verdict: Time Limit Exceeded):
def main():
    from bisect import bisect_left as bl, bisect_right as br, insort
    import sys
    import heapq
    # from math import *
    from collections import defaultdict as dd, deque
    def data():
        return sys.stdin.readline().strip()

    def mdata():
        return map(int, data().split())

    out = sys.stdout.write
    # sys.setrecursionlimit(100000)
    INF = int(10e9)

    s = data()
    t = data()
    dp = [[0] * (len(s) + 1) for i in range(len(t) + 1)]
    for i in range(1, len(t) + 1):
        for j in range(1, len(s) + 1):
            if s[j - 1] == t[i - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
            else:
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
    m = max(max(dp))
    ans = ''
    for i in range(len(t) - 1, -1, -1):
        for j in range(len(s) - 1, -1, -1):
            if dp[i + 1][j + 1] == m and s[j] == t[i]:
                ans = s[j] + ans
                m -= 1
                break
    out(ans+'\n')


if __name__ == '__main__':
    main()

Fixed submission:
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.buffer.readline().strip().decode()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp=[[0]*(len(s)+1) for i in range(len(t)+1)]
for i in range(1,len(t)+1):
    for j in range(1,len(s)+1):
        if s[j-1]==t[i-1]:
            dp[i][j]=dp[i-1][j-1]+1
        else:
            dp[i][j]=max(dp[i-1][j],dp[i][j-1])
m=max(max(dp))
ans=''
for i in range(len(t)-1,-1,-1):
    for j in range(len(s)-1,-1,-1):
        if dp[i+1][j+1]==m and s[j]==t[i]:
            ans=s[j]+ans
            m-=1
            break
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.readline().strip()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp1=[0]*len(s)
for i in range(len(t)):
    m=0
    for j in range(len(s)):
        if s[j]==t[i]:
            k=dp1[j]
            dp1[j]=m+1
            m=max(k,m)
        else:
            m=max(m,dp1[j])

dp2=[0]*len(s)
for i in range(len(t)-1,-1,-1):
    m=0
    for j in range(len(s)-1,-1,-1):
        if s[j]==t[i]:
            k=dp2[j]
            dp2[j]=m+1
            m=max(k,m)
        else:
            m=max(m,dp2[j])

m=max(dp1)
cnt=m
ans=''
for j in range(len(s)-1,-1,-1):
    if dp1[j]>=cnt and dp2[j]>=m-cnt+1:
        ans=s[j]+ans
        cnt-=1
print(ans)



Fixed submission:
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.buffer.readline().strip().decode()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp=[[0]*(len(s)+1) for i in range(len(t)+1)]
for i in range(1,len(t)+1):
    for j in range(1,len(s)+1):
        if s[j-1]==t[i-1]:
            dp[i][j]=dp[i-1][j-1]+1
        else:
            dp[i][j]=max(dp[i-1][j],dp[i][j-1])
m=max(max(dp))
ans=''
for i in range(len(t)-1,-1,-1):
    for j in range(len(s)-1,-1,-1):
        if dp[i+1][j+1]==m and s[j]==t[i]:
            ans=s[j]+ans
            m-=1
            break
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.readline().strip()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp1=[0]*len(s)
for i in range(len(t)):
    m=0
    dp2=dp1.copy()
    for j in range(len(s)):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp1[j])
        m=max(m,dp1[j])
    dp1=dp2.copy()

dp3=[0]*len(s)
for i in range(len(t)-1,-1,-1):
    m=0
    dp2=dp3.copy()
    for j in range(len(s)-1,-1,-1):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp3[j])
        m=max(m,dp3[j])
    dp3=dp2.copy()

m=max(dp1)
cnt=m
ans=''
for j in range(len(s)-1,-1,-1):
    if dp1[j]>=cnt and dp3[j]>=m-cnt+1:
        ans=s[j]+ans
        cnt-=1
    if cnt==0:
        break
print(ans)



Fixed submission:
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.buffer.readline().strip().decode()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp=[[0]*(len(s)+1) for i in range(len(t)+1)]
for i in range(1,len(t)+1):
    for j in range(1,len(s)+1):
        if s[j-1]==t[i-1]:
            dp[i][j]=dp[i-1][j-1]+1
        else:
            dp[i][j]=max(dp[i-1][j],dp[i][j-1])
m=max(max(dp))
ans=''
for i in range(len(t)-1,-1,-1):
    for j in range(len(s)-1,-1,-1):
        if dp[i+1][j+1]==m and s[j]==t[i]:
            ans=s[j]+ans
            m-=1
            break
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.readline().strip()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=input()
t=input()
dp1=[0]*len(s)
for i in range(len(t)):
    m=0
    dp2=dp1.copy()
    for j in range(len(s)):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp1[j])
        m=max(m,dp1[j])
    dp1=dp2.copy()

dp3=[0]*len(s)
for i in range(len(t)-1,-1,-1):
    m=0
    dp2=dp3.copy()
    for j in range(len(s)-1,-1,-1):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp3[j])
        m=max(m,dp3[j])
    dp3=dp2.copy()

m=max(dp1)
cnt=max(dp1)
ans=''
for j in range(len(s)-1,-1,-1):
    if dp1[j]>=cnt and dp3[j]>=m-cnt+1:
        ans=s[j]+ans
        cnt-=1
    if cnt==0:
        break
print(ans)



Fixed submission:
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.buffer.readline().strip().decode()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp=[[0]*(len(s)+1) for i in range(len(t)+1)]
for i in range(1,len(t)+1):
    for j in range(1,len(s)+1):
        if s[j-1]==t[i-1]:
            dp[i][j]=dp[i-1][j-1]+1
        else:
            dp[i][j]=max(dp[i-1][j],dp[i][j-1])
m=max(max(dp))
ans=''
for i in range(len(t)-1,-1,-1):
    for j in range(len(s)-1,-1,-1):
        if dp[i+1][j+1]==m and s[j]==t[i]:
            ans=s[j]+ans
            m-=1
            break
print(ans)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.readline().strip()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp1=[0]*len(s)
for i in range(len(t)):
    m=0
    dp2=dp1.copy()
    for j in range(len(s)):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp1[j])
        m=max(m,dp1[j])
    dp1=dp2.copy()

dp3=[0]*len(s)
for i in range(len(t)-1,-1,-1):
    m=0
    dp2=dp3.copy()
    for j in range(len(s)-1,-1,-1):
        if s[j]==t[i]:
            dp2[j]=max(m+1,dp3[j])
        m=max(m,dp3[j])
    dp3=dp2.copy()

m=max(dp1)
cnt=max(dp1)
ans=''
for j in range(len(s)-1,-1,-1):
    if dp1[j]>=cnt and dp3[j]>=m-cnt+1:
        ans=s[j]+ans
        cnt-=1
    if cnt==0:
        break
print(ans)



Fixed submission:
from bisect import bisect_left as bl, bisect_right as br, insort
import sys
import heapq
#from math import *
from collections import defaultdict as dd, deque
def data(): return sys.stdin.buffer.readline().strip().decode()
def mdata(): return map(int, data().split())
out=sys.stdout.write
#sys.setrecursionlimit(100000)
INF=int(10e9)


s=data()
t=data()
dp=[[0]*(len(s)+1) for i in range(len(t)+1)]
for i in range(1,len(t)+1):
    for j in range(1,len(s)+1):
        if s[j-1]==t[i-1]:
            dp[i][j]=dp[i-1][j-1]+1
        else:
            dp[i][j]=max(dp[i-1][j],dp[i][j-1])
m=max(max(dp))
ans=''
for i in range(len(t)-1,-1,-1):
    for j in range(len(s)-1,-1,-1):
        if dp[i+1][j+1]==m and s[j]==t[i]:
            ans=s[j]+ans
            m-=1
            break
print(ans)