Buggy python submission (verdict: Time Limit Exceeded):
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict, deque

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = il()
    SA = [0] * (N + 1)
    for n in range(N):
        SA[n + 1] = A[n] + SA[n]
    B = il()
    SB = [0] * (M + 1)
    for m in range(M):
        SB[m + 1] = B[m] + SB[m]
        
    ret = 0
    for n in range(N+1):
        for m in range(M+1):
            if SA[n] + SB[m] <= K:
                ret = max(ret, n + m)
    print(ret)


if __name__ == '__main__':
    main()


Fixed submission:
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict, deque

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = list(itertools.accumulate([0] + il()))
    B = list(itertools.accumulate(([0] + il())))

    ret, m = 0, M
    for n in range(N+1):
        if A[n] > K:
            break

        while B[m] > K - A[n]:
            m -= 1
        ret = max(ret, n+m)
    print(ret)




if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict, deque

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = il()
    SA = [0] * (N + 1)
    for n in range(N):
        SA[n + 1] = A[n] + SA[n]
    B = il()
    SB = [0] * (M + 1)
    for m in range(M):
        SB[m + 1] = B[m] + SA[m]

    ret = 0
    for n in range(N+1):
        for m in range(M+1):
            if SA[n] + SB[m] <= K:
                ret = max(ret, n + m)
    print(ret)


if __name__ == '__main__':
    main()


Fixed submission:
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict, deque

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = list(itertools.accumulate([0] + il()))
    B = list(itertools.accumulate(([0] + il())))

    ret, m = 0, M
    for n in range(N+1):
        if A[n] > K:
            break

        while B[m] > K - A[n]:
            m -= 1
        ret = max(ret, n+m)
    print(ret)




if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = il()
    B = il()
    aq, bq = 0, 0
    time, ret = 0, 0

    for _ in range(N+M):
        if aq < N and A[aq] < B[bq] and A[aq] + time <= K:
            time += A[aq]
            ret += 1
            aq += 1
        elif bq < M and B[bq] + time <= K:
            time += B[bq]
            ret += 1
            bq += 1
        else:
            break
    print(ret)


if __name__ == '__main__':
    main()


Fixed submission:
import sys, os, math, bisect, itertools, collections, heapq, queue
# from scipy.sparse.csgraph import csgraph_from_dense, floyd_warshall
from decimal import Decimal
from collections import defaultdict, deque

# import fractions

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)
# lcm = lambda x, y: (x * y) // fractions.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    N, M, K = il()
    A = list(itertools.accumulate([0] + il()))
    B = list(itertools.accumulate(([0] + il())))

    ret, m = 0, M
    for n in range(N+1):
        if A[n] > K:
            break

        while B[m] > K - A[n]:
            m -= 1
        ret = max(ret, n+m)
    print(ret)




if __name__ == '__main__':
    main()