Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
# encoding:utf-8
import copy
import random
import bisect #bisect_left　これで二部探索の大小検索が行える
import fractions #最小公倍数などはこっち
import math
import sys
import collections
from decimal import Decimal # 10進数で考慮できる

mod = 10**9+7
sys.setrecursionlimit(mod) # 再帰回数上限はでdefault1000

d = collections.deque()
def LI(): return list(map(int, sys.stdin.readline().split()))

"""
dp
time / books_no?
10 0 0
20 0 0
30 0 0
40 0 0
50 0 0
60 1 0
70 1 0
80 0 1




"""



N, M, K = LI()
A = LI()
B = LI()

"""
片方に注目して探索すればよい　

単純にfor,forだと計算量がまずいが，前回の値の部分から探索すればいいのでそこまで
計算量は増えない

"""

a = [0]
b = [0]

for i in range(N):
    a.append(a[-1] + A[i])

for i in range(M):
    b.append(b[-1] + B[i])

# print(a)
ans = 0
best = mod
for i in range(N + 1):
    if a[i] > K:
        break
    for j in range(min(best + 1, M + 1)):
        if a[i] + b[j] > K:
            break
        ans = max(ans, i + j)
        best = j
print(ans)
    

Fixed submission:
#!/usr/bin/env python3
# encoding:utf-8
import copy
import random
import bisect #bisect_left　これで二部探索の大小検索が行える
import fractions #最小公倍数などはこっち
import math
import sys
import collections
from decimal import Decimal # 10進数で考慮できる

mod = 10**9+7
sys.setrecursionlimit(mod) # 再帰回数上限はでdefault1000

d = collections.deque()
def LI(): return list(map(int, sys.stdin.readline().split()))

"""
dp
time / books_no?
10 0 0
20 0 0
30 0 0
40 0 0
50 0 0
60 1 0
70 1 0
80 0 1




"""



N, M, K = LI()
A = LI()
B = LI()

"""
片方に注目して探索すればよい　

単純にfor,forだと計算量がまずいが，前回の値の部分から探索すればいいのでそこまで
計算量は増えない

"""

a = [0]
b = [0]

for i in range(N):
    a.append(a[-1] + A[i])

for i in range(M):
    b.append(b[-1] + B[i])

# print(a)
ans = 0
j = M
for i in range(N + 1):
    if a[i] > K:
        break
    while b[j] > K - a[i]:
        j -= 1
    ans = max(ans, i + j)
print(ans)

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
# encoding:utf-8
import copy
import random
import bisect #bisect_left　これで二部探索の大小検索が行える
import fractions #最小公倍数などはこっち
import math
import sys
import collections
from decimal import Decimal # 10進数で考慮できる

mod = 10**9+7
sys.setrecursionlimit(mod) # 再帰回数上限はでdefault1000

d = collections.deque()
def LI(): return list(map(int, sys.stdin.readline().split()))

"""
dp
time / books_no?
10 0 0
20 0 0
30 0 0
40 0 0
50 0 0
60 1 0
70 1 0
80 0 1




"""



N, M, K = LI()
A = LI()
B = LI()

a = [0 for i in range(2 * 10 ** 5)]
b = [0 for i in range(2 * 10 ** 5)]
a_sum = [0 for i in range(2 * 10**5)]
b_sum = [0 for i in range(2 * 10 ** 5)]

time = 0
sum_a = 0
for i in range(N):
    time += A[i]
    if time > 2 * 10 ** 5:
        break
    a[time] += 1

time = 0
for j in range(M):
    time += B[j]
    if time > 2 * 10 ** 5:
        break
    b[time] += 1

s_a = 0
s_b = 0
for time in range(2*10 **5):
    s_a += a[time]
    a_sum[time] = s_a
    s_b += b[time]
    b_sum[time] = s_b

ans = 0
for i in range(K):
    ans = max(ans, a_sum[i] + b_sum[K - i])
print(ans)

Fixed submission:
#!/usr/bin/env python3
# encoding:utf-8
import copy
import random
import bisect #bisect_left　これで二部探索の大小検索が行える
import fractions #最小公倍数などはこっち
import math
import sys
import collections
from decimal import Decimal # 10進数で考慮できる

mod = 10**9+7
sys.setrecursionlimit(mod) # 再帰回数上限はでdefault1000

d = collections.deque()
def LI(): return list(map(int, sys.stdin.readline().split()))

"""
dp
time / books_no?
10 0 0
20 0 0
30 0 0
40 0 0
50 0 0
60 1 0
70 1 0
80 0 1




"""



N, M, K = LI()
A = LI()
B = LI()

"""
片方に注目して探索すればよい　

単純にfor,forだと計算量がまずいが，前回の値の部分から探索すればいいのでそこまで
計算量は増えない

"""

a = [0]
b = [0]

for i in range(N):
    a.append(a[-1] + A[i])

for i in range(M):
    b.append(b[-1] + B[i])

# print(a)
ans = 0
j = M
for i in range(N + 1):
    if a[i] > K:
        break
    while b[j] > K - a[i]:
        j -= 1
    ans = max(ans, i + j)
print(ans)