Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10 ** 9 + 7

dp = [[0] * (c + 1) for i in range(n + 1)]
dp[0][0] = 1

ru = [[0] * 410 for i in range(410)]
for cnt in range(410):
    for x in range(409):
        ru[cnt][x + 1] += ru[cnt][x] + pow(x, cnt, MOD)
      
for ni in range(n):
    for cnt in range(c + 1):
        for ci in range(cnt, c + 1):
            dp[ni + 1][ci] += (ru[cnt][b[ni] + 1] - ru[cnt][a[ni]]) * dp[ni][ci - cnt] 
            dp[ni + 1][ci] %= MOD
print(dp[-1][-1])

Fixed submission:
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10**9 + 7

dp = [[0]*(c+1) for i in range(n+1)]
dp[0][0] = 1

ruiseki = [[0] * (410) for _ in range(c+1)]
for i in range(c + 1):
    for j in range(409):
        ruiseki[i][j + 1] = ruiseki[i][j] + pow(j, i, MOD)
        ruiseki[i][j + 1] %= MOD
  
for i in range(n):
    for all_num in range(c + 1):
        for j in range(all_num + 1):
            # i番目の子供に、j個の飴を配る
            dp[i+1][all_num] += (ruiseki[j][b[i]+1] - ruiseki[j][a[i]]) * dp[i][all_num - j]
            dp[i+1][all_num] %= MOD
print(dp[-1][-1])

Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10 ** 9 + 7

dp = [[0] * (c + 1) for i in range(n + 1)]
dp[0][0] = 1

for ni in range(n):
    for cnt in range(c + 1):
        ru = 0
        for x in range(a[ni], b[ni] + 1):
            ru += pow(x, cnt, MOD)
            ru %= MOD
        for ci in range(cnt, c + 1):
            dp[ni + 1][ci] += ru * dp[ni][ci - cnt] 
            dp[ni + 1][ci] %= MOD
print(dp[-1][-1])

Fixed submission:
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10**9 + 7

dp = [[0]*(c+1) for i in range(n+1)]
dp[0][0] = 1

ruiseki = [[0] * (410) for _ in range(c+1)]
for i in range(c + 1):
    for j in range(409):
        ruiseki[i][j + 1] = ruiseki[i][j] + pow(j, i, MOD)
        ruiseki[i][j + 1] %= MOD
  
for i in range(n):
    for all_num in range(c + 1):
        for j in range(all_num + 1):
            # i番目の子供に、j個の飴を配る
            dp[i+1][all_num] += (ruiseki[j][b[i]+1] - ruiseki[j][a[i]]) * dp[i][all_num - j]
            dp[i+1][all_num] %= MOD
print(dp[-1][-1])

Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10 ** 9 + 7

dp = [[0] * (c + 1) for i in range(n + 1)]
dp[0][0] = 1

for ni in range(n):
    for cnt in range(c + 1):
        ru = 0
        for x in range(a[ni], b[ni] + 1):
            ru += pow(x, cnt, MOD)
            ru %= MOD
        for ci in range(c + 1):
            if ci - cnt < 0:
                continue
            dp[ni + 1][ci] += ru * dp[ni][ci - cnt] 
            dp[ni + 1][ci] %= MOD
print(dp[-1][-1])

Fixed submission:
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10**9 + 7

dp = [[0]*(c+1) for i in range(n+1)]
dp[0][0] = 1

ruiseki = [[0] * (410) for _ in range(c+1)]
for i in range(c + 1):
    for j in range(409):
        ruiseki[i][j + 1] = ruiseki[i][j] + pow(j, i, MOD)
        ruiseki[i][j + 1] %= MOD
  
for i in range(n):
    for all_num in range(c + 1):
        for j in range(all_num + 1):
            # i番目の子供に、j個の飴を配る
            dp[i+1][all_num] += (ruiseki[j][b[i]+1] - ruiseki[j][a[i]]) * dp[i][all_num - j]
            dp[i+1][all_num] %= MOD
print(dp[-1][-1])

Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10**9 + 7

dp = [[0]*(c+1) for i in range(n+1)]
dp[0][0] = 1

# forループを更に一つ潰す必要あり
for i in range(n):
    for x in range(a[i], b[i] + 1):
        for all_num in range(c+1):
            for j in range(all_num + 1):
                # i番目の子供に、j個の飴を配る
                dp[i+1][all_num] += x**j * dp[i][all_num - j]
                dp[i+1][all_num] %= MOD
print(dp[-1][-1])

Fixed submission:
n, c = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
MOD = 10**9 + 7

dp = [[0]*(c+1) for i in range(n+1)]
dp[0][0] = 1

ruiseki = [[0] * (410) for _ in range(c+1)]
for i in range(c + 1):
    for j in range(409):
        ruiseki[i][j + 1] = ruiseki[i][j] + pow(j, i, MOD)
        ruiseki[i][j + 1] %= MOD
  
for i in range(n):
    for all_num in range(c + 1):
        for j in range(all_num + 1):
            # i番目の子供に、j個の飴を配る
            dp[i+1][all_num] += (ruiseki[j][b[i]+1] - ruiseki[j][a[i]]) * dp[i][all_num - j]
            dp[i+1][all_num] %= MOD
print(dp[-1][-1])