Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 6)

n,m,k = map(int,input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
a.append(1)
b.append(1)
ans = 0

def dfs(time,count,i,j):
    global ans,n,m,k,a,b
    if (i == n or time + a[i] > k) and (j == m or time + b[j] > k):
        ans = max(ans, count)
    else:
        if i <= n-1 and time + a[i] <= k:
            dfs(time + a[i],count + 1,i+1,j)
        if j <= m-1 and time + b[j] <= k:
           dfs(time + b[j],count + 1,i,j+1)  

shoki_time = 0
shoki_count = 0
shoki_i = 0
shoki_j = 0
dfs(shoki_time,shoki_count,shoki_i,shoki_j)
print(ans)

Fixed submission:
n,m,k=map(int,input().split())
arr1=list(map(int,input().split()))
arr2=list(map(int,input().split()))
acum1=[0]
for i in range(n): #累積和ai,bjを求める
 acum1.append(acum1[-1]+arr1[i])
acum2=[0]
for i in range(m):
 acum2.append(acum2[-1]+arr2[i])
ans=0
j=m
for i in range(n+1):
 if acum1[i]>k: #ai>Kであれば、どのようにjを選んでもai+bj<=Kとなることはないので探索を終了する
   break
 while acum2[j]>k-acum1[i] and j>0: #各iについて、bj<=K-aiを満たす最大のjを求める
   j-=1
 ans=max(ans,i+j)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 6)

n,m,k = map(int,input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
a.append(1)
b.append(1)
ans = 0

def dfs(time,count,i,j):
    global ans,n,m,k,a,b
    if i <= n-1 and time + a[i] <= k:
            dfs(time + a[i],count + 1,i+1,j)
    if j <= m-1 and time + b[j] <= k:
           dfs(time + b[j],count + 1,i,j+1)  
    if (i == n or time + a[i] > k) and (j == m or time + b[j] > k):
        ans = max(ans, count)

shoki_time = 0
shoki_count = 0
shoki_i = 0
shoki_j = 0
dfs(shoki_time,shoki_count,shoki_i,shoki_j)
print(ans)

Fixed submission:
n,m,k=map(int,input().split())
arr1=list(map(int,input().split()))
arr2=list(map(int,input().split()))
acum1=[0]
for i in range(n): #累積和ai,bjを求める
 acum1.append(acum1[-1]+arr1[i])
acum2=[0]
for i in range(m):
 acum2.append(acum2[-1]+arr2[i])
ans=0
j=m
for i in range(n+1):
 if acum1[i]>k: #ai>Kであれば、どのようにjを選んでもai+bj<=Kとなることはないので探索を終了する
   break
 while acum2[j]>k-acum1[i] and j>0: #各iについて、bj<=K-aiを満たす最大のjを求める
   j-=1
 ans=max(ans,i+j)
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 6)

n,m,k = map(int,input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
a.append(1)
b.append(1)
ans = 0

def dfs(time,count,i,j):
    global ans,n,m,k,a,b
    if i <= n-1:
        if time + a[i] <= k:
            dfs(time + a[i],count + 1,i+1,j)
    if j <= m-1:
        if time + b[j] <= k:
           dfs(time + b[j],count + 1,i,j+1)  
    if (i == n or time + a[i] > k) and (j == m or time + b[j] > k):
        ans = max(ans, count)

shoki_time = 0
shoki_count = 0
shoki_i = 0
shoki_j = 0
dfs(shoki_time,shoki_count,shoki_i,shoki_j)
print(ans)

Fixed submission:
n,m,k=map(int,input().split())
arr1=list(map(int,input().split()))
arr2=list(map(int,input().split()))
acum1=[0]
for i in range(n): #累積和ai,bjを求める
 acum1.append(acum1[-1]+arr1[i])
acum2=[0]
for i in range(m):
 acum2.append(acum2[-1]+arr2[i])
ans=0
j=m
for i in range(n+1):
 if acum1[i]>k: #ai>Kであれば、どのようにjを選んでもai+bj<=Kとなることはないので探索を終了する
   break
 while acum2[j]>k-acum1[i] and j>0: #各iについて、bj<=K-aiを満たす最大のjを求める
   j-=1
 ans=max(ans,i+j)
print(ans)