12:17 (UTC): The sample input 1 and 2 were swapped. The error is now fixed. We are very sorry for your inconvenience.
There are N children in AtCoder Kindergarten, conveniently numbered 1 through N. Mr. Evi will distribute C indistinguishable candies to the children.
If child i is given a candies, the child's happiness will become x_i^a, where x_i is the child's excitement level. The activity level of the kindergarten is the product of the happiness of all the N children.
For each possible way to distribute C candies to the children by giving zero or more candies to each child, calculate the activity level of the kindergarten. Then, calculate the sum over all possible way to distribute C candies. This sum can be seen as a function of the children's excitement levels x_1,..,x_N, thus we call it f(x_1,..,x_N).
You are given integers A_i,B_i (1≦i≦N). Find  modulo 10^9+7.

-----Constraints-----
 - 1≦N≦400
 - 1≦C≦400
 - 1≦A_i≦B_i≦400 (1≦i≦N)

-----Partial Score-----
 - 400 points will be awarded for passing the test set satisfying A_i=B_i (1≦i≦N).

-----Input-----
The input is given from Standard Input in the following format:
N C
A_1 A_2 ... A_N
B_1 B_2 ... B_N

-----Output-----
Print the value of  modulo 10^9+7.

-----Sample Input-----
2 3
1 1
1 1

-----Sample Output-----
4

This case is included in the test set for the partial score, since A_i=B_i.
We only have to consider the sum of the activity level of the kindergarten where the excitement level of both child 1 and child 2 are 1 (f(1,1)).
 - If child 1 is given 0 candy, and child 2 is given 3 candies, the activity level of the kindergarten is 1^0*1^3=1.
 - If child 1 is given 1 candy, and child 2 is given 2 candies, the activity level of the kindergarten is 1^1*1^2=1.
 - If child 1 is given 2 candies, and child 2 is given 1 candy, the activity level of the kindergarten is 1^2*1^1=1.
 - If child 1 is given 3 candies, and child 2 is given 0 candy, the activity level of the kindergarten is 1^3*1^0=1.
Thus, f(1,1)=1+1+1+1=4, and the sum over all f is also 4.

Difficulty: HARD

Solutions:
from collections import defaultdict, deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random

def LI():
	return [int(x) for x in sys.stdin.readline().split()]

def I():
	return int(sys.stdin.readline())

def LS():
	return [list(x) for x in sys.stdin.readline().split()]

def S():
	res = list(sys.stdin.readline())
	if res[-1] == '\n':
		return res[:-1]
	return res

def IR(n):
	return [I() for i in range(n)]

def LIR(n):
	return [LI() for i in range(n)]

def SR(n):
	return [S() for i in range(n)]

def LSR(n):
	return [LS() for i in range(n)]
sys.setrecursionlimit(1000000)
mod = 1000000007

def A():
	return

def B():
	return

def C():
	(n, c) = LI()
	a = LI()
	b = LI()
	s = [[0] * (c + 1) for i in range(n)]
	for i in range(n):
		(ai, bi) = (a[i], b[i])
		for x in range(ai, bi + 1):
			e = 1
			for k in range(c + 1):
				s[i][k] += e
				if s[i][k] >= mod:
					s[i][k] %= mod
				e *= x
				if e >= mod:
					e %= mod
	dp = [[0] * (c + 1) for i in range(n)]
	for k in range(c + 1):
		dp[0][k] = s[0][k]
	for i in range(1, n):
		for k in range(c + 1):
			for j in range(k + 1):
				dp[i][k] += dp[i - 1][j] * s[i][k - j]
				if dp[i][k] >= mod:
					dp[i][k] %= mod
	print(dp[-1][c])
	return

def D():
	return

def E():
	return

def F():
	return
C()


import sys
input = sys.stdin.readline
import numpy as np
MOD = 10 ** 9 + 7
(N, C) = list(map(int, input().split()))
A = [int(x) for x in input().split()]
B = [int(x) for x in input().split()]
kth_pow = np.ones((C + 1, 401), dtype=np.int64)
rng = np.arange(401, dtype=np.int64)
for i in range(1, C + 1):
	kth_pow[i] = kth_pow[i - 1] * rng % MOD
kth_pow_cum = kth_pow.cumsum(axis=1) % MOD
dp = np.zeros(C + 1, dtype=np.int64)
dp[0] = 1
for (a, b) in zip(A, B):
	arr = kth_pow_cum[:, b] - kth_pow_cum[:, a - 1]
	prev = dp
	dp = np.zeros(C + 1, dtype=np.int64)
	for n in range(C + 1):
		dp[n:] += arr[n] * prev[:C + 1 - n] % MOD
	dp %= MOD
answer = dp[C]
print(answer)


mod = 10 ** 9 + 7
(N, C) = list(map(int, input().split()))
A = list(map(int, input().split()))
B = list(map(int, input().split()))
dp = [[0] * (C + 1) for i in range(N + 1)]
dp[-1][0] = 1
S = [[0] * (C + 1) for _ in range(N + 1)]
for i in range(N):
	power = [1] * (400 + 1)
	for j in range(C + 1):
		for x in range(A[i], B[i] + 1):
			S[i][j] += power[x]
			S[i][j] %= mod
			power[x] *= x
			power[x] %= mod
for i in range(N):
	for j in range(C + 1):
		for k in range(j + 1):
			dp[i][j] += dp[i - 1][j - k] * S[i][k]
			dp[i][j] %= mod
print(dp[-2][-1])


import math
import queue
import bisect
from collections import deque, defaultdict
import heapq as hpq
from sys import stdin, setrecursionlimit
ipt = stdin.readline
setrecursionlimit(10 ** 7)
mod = 10 ** 9 + 7

def main():
	(n, c) = map(int, ipt().split())
	a = [int(i) for i in ipt().split()]
	b = [int(i) for i in ipt().split()]
	nj = [[] for j in range(c + 1)]
	nj[0] = [1] * 401
	for j in range(1, c + 1):
		for i in range(401):
			nj[j].append(nj[j - 1][i] * i % mod)
	snj = [[0] for j in range(c + 1)]
	for j in range(c + 1):
		sj = snj[j]
		ssj = nj[j]
		for i in range(1, 401):
			sj.append((sj[-1] + ssj[i]) % mod)
	dp = [snj[k][b[0]] - snj[k][a[0] - 1] for k in range(c + 1)]
	for i in range(1, n):
		ai = a[i]
		bi = b[i]
		for j in range(c, -1, -1):
			dp[j] = dp[j] * (bi - ai + 1) % mod
			for k in range(1, j + 1):
				dp[j] = (dp[j] + dp[j - k] * (snj[k][bi] - snj[k][ai - 1])) % mod
	print(dp[c] % mod)
	return None
main()


(N, C) = map(int, input().split())
A = [int(i) for i in input().split()]
B = [int(i) for i in input().split()]
mod = 10 ** 9 + 7
exponen = [[0 for j in range(401)] for i in range(401)]
for i in range(401):
	exponen[i][0] = 1
	for j in range(400):
		exponen[i][j + 1] = exponen[i][j] * i % mod
expsum = [[0 for j in range(401)] for i in range(402)]
for j in range(401):
	for i in range(401):
		expsum[i + 1][j] = (expsum[i][j] + exponen[i][j]) % mod
func = [[0 for j in range(C + 1)] for i in range(N)]
dp = [[0 for j in range(C + 1)] for i in range(N + 1)]
dp[0][0] = 1
for i in range(N):
	for j in range(C + 1):
		func[i][j] = (expsum[B[i] + 1][j] - expsum[A[i]][j]) % mod
for i in range(N):
	for x in range(C + 1):
		for y in range(C + 1):
			if x + y > C:
				continue
			dp[i + 1][x + y] += dp[i][x] * func[i][y]
			dp[i + 1][x + y] %= mod
print(dp[N][C])


import sys
input = sys.stdin.readline
sys.setrecursionlimit(pow(10, 6))
MOD = pow(10, 9) + 7

def main():
	(n, c) = map(int, input().split())
	a = list(map(int, input().split()))
	b = list(map(int, input().split()))
	abc = [[0 for _ in range(401)] for _ in range(401)]
	for i in range(401):
		abc[0][i] = 1
	abc[0][0] = 0
	for i in range(1, 401):
		for j in range(1, 401):
			abc[j][i] = abc[j - 1][i] * i % MOD
	for i in range(1, 401):
		for j in range(401):
			abc[j][i] += abc[j][i - 1]
			if abc[j][i] >= MOD:
				abc[j][i] -= MOD
	dp = [[0 for _ in range(c + 1)] for _ in range(n + 1)]
	dp[0][0] = 1
	for i in range(1, n + 1):
		for j in range(c + 1):
			for k in range(j + 1):
				accm = abc[k][b[i - 1]] - abc[k][a[i - 1] - 1]
				if accm < 0:
					accm += MOD
				dp[i][j] += dp[i - 1][j - k] * accm % MOD
				if dp[i][j] >= MOD:
					dp[i][j] -= MOD
	print(dp[n][c])
main()


MOD = 10 ** 9 + 7
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
P = [[1] for _ in range(401)]
for _ in range(1, 401):
	for i in range(1, 401):
		P[i].append(P[i][-1] * i % MOD)
R = [[] for _ in range(N)]
for (i, AB) in enumerate(zip(A, B)):
	(AA, BB) = AB
	for a in range(401):
		tmp = 0
		for x in range(AA, BB + 1):
			tmp += P[x][a]
			tmp %= MOD
		R[i].append(tmp)
dp = [[0] * (C + 1) for _ in range(N + 1)]
dp[0][0] = 1
for n in range(1, N + 1):
	for k in range(C + 1):
		for l in range(k + 1):
			dp[n][k] += dp[n - 1][k - l] * R[n - 1][l]
			dp[n][k] %= MOD
print(dp[N][C])


import numpy as np
(N, C) = list(map(int, input().split()))
A = list(map(int, input().split()))
B = list(map(int, input().split()))
mod = 10 ** 9 + 7
P = np.empty((404, 404), dtype=np.int64)
P[0, :] = 1
ar = np.arange(404, dtype=np.int64)
for i in range(1, 404):
	P[i] = P[i - 1] * ar % mod
P = P.cumsum(axis=1, dtype=np.int64) % mod
P = P.T
dp = np.zeros(C + 1, dtype=np.int64)
dp[0] = 1
for (a, b) in zip(A, B):
	dp_new = np.zeros(C + 1, dtype=np.int64)
	p = (P[b] - P[a - 1]) % mod
	for c in range(C + 1):
		dp_new[c] = (dp[:c + 1] * p[c::-1] % mod).sum()
	dp = dp_new % mod
print(dp[C])


import sys
from itertools import accumulate
readline = sys.stdin.readline
MOD = 10 ** 9 + 7
(N, C) = map(int, readline().split())
A = [0] + list(map(int, readline().split()))
B = [0] + list(map(int, readline().split()))
acsq = []
lb = max(B) + 1
for j in range(C + 1):
	ac = [0] * lb
	ac[0] = 1
	for i in range(1, lb):
		ac[i] = (ac[i - 1] + pow(i, j, MOD)) % MOD
	acsq.append(ac)
dp = [[0] * (C + 1) for _ in range(N + 1)]
dp[0][0] = 1
for i in range(1, N + 1):
	(a, b) = (A[i], B[i])
	for c in range(C + 1):
		res = 0
		for j in range(c + 1):
			res = (res + (acsq[c - j][b] - acsq[c - j][a - 1]) * dp[i - 1][j]) % MOD
		dp[i][c] = res
print(dp[N][C])


import sys
(N, C) = map(int, input().split())
A = [int(i) for i in input().split()]
B = [int(i) for i in input().split()]
mod = 10 ** 9 + 7
table = [[pow(j, i, mod) for j in range(405)] for i in range(405)]
ntable = [[0] * 405 for i in range(405)]
for i in range(405):
	t = 0
	for j in range(1, 405):
		t += table[i][j]
		t %= mod
		ntable[i][j] = t
F = [B[i] - A[i] + 1 for i in range(N)]
G = [0] * N
t = 1
for i in range(N):
	t *= F[i]
	t %= mod
for i in range(N):
	G[i] = t * pow(F[i], mod - 2, mod) % mod
dp = [[0] * (C + 1) for i in range(N)]
for i in range(C + 1):
	dp[0][i] = (ntable[i][B[0]] - ntable[i][A[0] - 1]) % mod
for i in range(1, N):
	for k in range(C + 1):
		for l in range(k + 1):
			dp[i][k] += dp[i - 1][l] * (ntable[k - l][B[i]] - ntable[k - l][A[i] - 1])
			dp[i][k] %= mod
print(dp[N - 1][C])


mod = 10 ** 9 + 7
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

def rev(X):
	return pow(X, mod - 2, mod)
pow_sum = [[B[i] - A[i] + 1 for j in range(C + 1)] for i in range(N)]
pow_table = [[1 for j in range(401)] for i in range(401)]
for i in range(401):
	for j in range(401):
		pow_table[i][j] = pow(i, j, mod)
for cnt in range(C):
	for i in range(N):
		pow_sum[i][cnt + 1] = 0
		for j in range(A[i], B[i] + 1):
			pow_sum[i][cnt + 1] += pow_table[j][cnt + 1]
		pow_sum[i][cnt + 1] %= mod
ans_dp = [[0 for i in range(C + 1)] for j in range(N + 1)]
ans_dp[0][0] = 1
for n in range(1, N + 1):
	for c in range(C + 1):
		for k in range(c + 1):
			ans_dp[n][c] += ans_dp[n - 1][k] * pow_sum[n - 1][c - k]
		ans_dp[n][c] %= mod
print(ans_dp[N][C] % mod)


(n, c) = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
mod = pow(10, 9) + 7
powlist = [[1] * 405 for _ in range(405)]
for i in range(1, 405):
	for j in range(1, 405):
		powlist[i][j] = j * powlist[i - 1][j] % mod
for i in range(405):
	for j in range(1, 405):
		powlist[i][j] += powlist[i][j - 1]
		powlist[i][j] %= mod
x = [[0] * (c + 1) for _ in range(n + 1)]
for i in range(1, n + 1):
	for j in range(c + 1):
		x[i][j] = powlist[j][b[i - 1]] - powlist[j][a[i - 1] - 1]
		x[i][j] %= mod
dp = [[0] * (c + 1) for _ in range(n + 1)]
dp[0][0] = 1
for i in range(1, n + 1):
	for j in range(c + 1):
		s = 0
		for k in range(j + 1):
			s += dp[i - 1][k] * x[i][j - k]
			s %= mod
		dp[i][j] = s
ans = dp[n][c]
print(ans)


(n, c) = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
mod = 10 ** 9 + 7
ex400 = [[1] * 401 for _ in range(401)]
for i in range(2, 401):
	for j in range(1, 401):
		ex400[i][j] = ex400[i][j - 1] * i % mod
cumsum400 = [[1] * 401 for _ in range(401)]
for i in range(1, 401):
	for j in range(401):
		cumsum400[i][j] = (cumsum400[i - 1][j] + ex400[i][j]) % mod
dp = [[0] * (c + 1) for _ in range(n + 1)]
dp[0][0] = 1
for i in range(1, n + 1):
	for j in range(c + 1):
		for k in range(j + 1):
			dp[i][j] += dp[i - 1][j - k] * (cumsum400[b[i - 1]][k] - cumsum400[a[i - 1] - 1][k])
			dp[i][j] %= mod
print(dp[-1][-1])


(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
DP = [[0] * (C + 1) for i in range(N + 1)]
DP[0][0] = 1
mod = 10 ** 9 + 7
X = [[0] for i in range(401)]
for i in range(401):
	for j in range(401):
		X[i].append((X[i][j] + pow(j, i, mod)) % mod)
for i in range(N):
	for j in range(C + 1):
		for k in range(j + 1):
			DP[i + 1][j] = (DP[i][j - k] * (X[k][B[i] + 1] - X[k][A[i]]) + DP[i + 1][j]) % mod
print(DP[N][C])


from collections import defaultdict, deque, Counter
from heapq import heappush, heappop, heapify
import math
import bisect
import random
from itertools import permutations, accumulate, combinations, product
import sys
import string
from bisect import bisect_left, bisect_right
from math import factorial, ceil, floor
from operator import mul
from functools import reduce
import pprint
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 20

def LI():
	return list(map(int, sys.stdin.buffer.readline().split()))

def I():
	return int(sys.stdin.buffer.readline())

def LS():
	return sys.stdin.buffer.readline().rstrip().decode('utf-8').split()

def S():
	return sys.stdin.buffer.readline().rstrip().decode('utf-8')

def IR(n):
	return [I() for i in range(n)]

def LIR(n):
	return [LI() for i in range(n)]

def SR(n):
	return [S() for i in range(n)]

def LSR(n):
	return [LS() for i in range(n)]

def SRL(n):
	return [list(S()) for i in range(n)]

def MSRL(n):
	return [[int(j) for j in list(S())] for i in range(n)]
mod = 1000000007
(n, c) = LI()
A = LI()
B = LI()
pre_compute = [[0] * 401 for _ in range(401)]
for ii in range(401):
	for jj in range(401):
		pre_compute[ii][jj] = pre_compute[ii - 1][jj]
		pre_compute[ii][jj] += pow(ii, jj, mod)
		pre_compute[ii][jj] %= mod
dp = [[0] * (c + 1) for _ in range(n + 1)]
dp[0][0] = 1
for i in range(n):
	for j in range(c + 1):
		for k in range(j + 1):
			dp[i + 1][j] += dp[i][k] * (pre_compute[B[i]][j - k] - pre_compute[A[i] - 1][j - k]) % mod
			dp[i + 1][j] %= mod
print(dp[n][c])


(n, c) = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
ab = list(zip(a, b))
table = [[0 for i in range(c + 1)] for j in range(401)]
mod = 10 ** 9 + 7
for j in range(c + 1):
	if j == 0:
		for i in range(401):
			table[i][j] = 1
	else:
		for i in range(401):
			table[i][j] = table[i][j - 1] * i % mod
dp = [[0 for i in range(c + 1)] for j in range(n + 1)]
for i in range(c + 1):
	dp[0][i] = 1
for i in range(1, n + 1):
	(a, b) = ab[i - 1]
	for j in range(a, b + 1):
		for k in range(c + 1):
			dp[i][k] = (dp[i][k] + table[j][k]) % mod
ans = [[0 for i in range(c + 1)] for j in range(n + 1)]
ans[0][0] = 1
for i in range(1, n + 1):
	for j in range(c + 1):
		for k in range(j + 1):
			ans[i][j] = (ans[i][j] + dp[i][k] * ans[i - 1][j - k]) % mod
print(ans[n][c])


MOD = 10 ** 9 + 7
(n, c) = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
sig = [[0 for _ in range(max(b) + 1)] for _ in range(c + 1)]
for i in range(c + 1):
	for j in range(1, max(b) + 1):
		sig[i][j] = sig[i][j - 1] + pow(j, i, MOD)
		sig[i][j] %= MOD

def sigma(C, A, B):
	return (sig[C][B] - sig[C][A - 1]) % MOD
dp = [[0 for _ in range(c + 1)] for _ in range(n)]
for j in range(c + 1):
	dp[0][j] = sigma(j, a[0], b[0])
for i in range(1, n):
	for j in range(c + 1):
		for k in range(j + 1):
			dp[i][j] += dp[i - 1][k] * sigma(j - k, a[i], b[i])
			dp[i][j] %= MOD
print(dp[n - 1][c])


(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
MOD = 10 ** 9 + 7

def gen_poly(a, b, c):
	poly = [0 for _ in range(c + 1)]
	for x in range(a, b + 1):
		xpow = 1
		for i in range(c + 1):
			poly[i] += xpow
			xpow = xpow * x % MOD
	for i in range(c + 1):
		poly[i] %= MOD
	return poly

def mult_polys(p1, p2, dmax):
	ans = [0 for _ in range(dmax + 1)]
	for (i, c) in enumerate(p1):
		for (i2, c2) in enumerate(p2):
			if i + i2 <= dmax:
				ans[i + i2] += c * c2
			else:
				break
	ans = [x % MOD for x in ans]
	return ans
polys = [gen_poly(a, b, C) for (a, b) in zip(A, B)]
prodpoly = [1]
for poly in polys:
	prodpoly = mult_polys(prodpoly, poly, C)
print(prodpoly[C])


(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
Mod = 10 ** 9 + 7
B_max = max(B)
P = [[0] * (C + 1) for _ in range(B_max + 1)]
for x in range(B_max + 1):
	E = P[x]
	E[0] = 1
	t = 1
	for k in range(1, C + 1):
		E[k] = t = t * x % Mod
T = []
for i in range(N):
	U = [0] * (C + 1)
	for x in range(A[i], B[i] + 1):
		for k in range(C + 1):
			U[k] += P[x][k]
			U[k] %= Mod
	T.append(U)
P = [1] + [0] * C
for Q in T:
	X = [0] * (C + 1)
	for i in range(C + 1):
		for j in range(C + 1):
			if i + j > C:
				break
			X[i + j] += P[i] * Q[j]
			X[i + j] %= Mod
	P = X.copy()
print(X[C])


def main(N, C, A, B):
	import sys
	input = sys.stdin.readline
	mod = 10 ** 9 + 7
	powA = [[0] * 401 for i in range(401)]
	for i in range(401):
		for j in range(401):
			powA[i][j] = pow(i, j, mod)
	S = [[0] * 401 for i in range(C + 1)]
	for i in range(C + 1):
		S[i][0] = 0
	for i in range(C + 1):
		for j in range(1, 401):
			S[i][j] = (S[i][j - 1] + powA[j][i]) % mod
	dp = [[0] * (C + 1) for i in range(N)]
	for i in range(C + 1):
		dp[0][i] = S[i][B[0]] - S[i][A[0] - 1]
	for i in range(1, N):
		for j in range(C + 1):
			tmp = 0
			for k in range(j + 1):
				tmp = (tmp + (S[k][B[i]] - S[k][A[i] - 1]) * dp[i - 1][j - k]) % mod
			dp[i][j] = tmp
	print(dp[N - 1][C])

def main2(N, C, A, B):
	import sys
	input = sys.stdin.readline
	mod = 10 ** 9 + 7
	powA = [[0] * 401 for i in range(401)]
	for i in range(401):
		for j in range(401):
			powA[i][j] = pow(i, j, mod)
	S = [[0] * 400 for i in range(C + 1)]
	for i in range(C + 1):
		S[i][0] = 1
	for i in range(C + 1):
		for j in range(1, 400):
			S[i][j] = (S[i][j - 1] + powA[j + 1][i]) % mod
	dp = [[0] * (C + 1) for i in range(N)]
	for i in range(C + 1):
		dp[0][i] = pow(A[0], i, mod)
	for i in range(1, N):
		for j in range(C + 1):
			tmp = 0
			for k in range(j + 1):
				tmp = (tmp + powA[A[i]][k] * dp[i - 1][j - k]) % mod
			dp[i][j] = tmp
	print(dp[N - 1][C])
import sys
input = sys.stdin.readline
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
if A == B:
	main2(N, C, A, B)
else:
	main(N, C, A, B)


mod = 10 ** 9 + 7
table = [[0 for i in range(401)] for j in range(401)]
for i in range(401):
	S = 0
	for j in range(1, 401):
		S += pow(j, i, mod)
		S %= mod
		table[i][j] = S
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
dp = [[0 for i in range(C + 1)] for j in range(N)]
for i in range(C + 1):
	dp[0][i] = table[i][B[0]] - table[i][A[0] - 1]
	dp[0][i] %= mod
for i in range(1, N):
	for j in range(C + 1):
		dp[i][j] = sum((dp[i - 1][j - k] * (table[k][B[i]] - table[k][A[i] - 1]) for k in range(j + 1)))
		dp[i][j] %= mod
print(dp[N - 1][C])


import sys
input = sys.stdin.readline
import numpy as np
MOD = 10 ** 9 + 7
(n, c) = map(int, input().split())
A = np.array(tuple(map(int, input().split())))
B = np.array(tuple(map(int, input().split())))
E = np.zeros((n, c + 1), dtype=np.int64)
for j in range(c + 1):
	cum = np.array(tuple((pow(k, j, MOD) for k in range(401)))).cumsum() % MOD
	E[:, j] = cum[B] - cum[A - 1]
dp = np.zeros((n + 1, c + 1), dtype=np.int64)
dp[0, 0] = 1
for (i, e) in enumerate(E):
	for (j, f) in enumerate(e):
		dp[i + 1, j:] += dp[i, :c + 1 - j] * f
		dp[i + 1] %= MOD
ans = dp[n, c]
print(ans)


MOD = 10 ** 9 + 7
(n, m) = [int(item) for item in input().split()]
a = [int(item) for item in input().split()]
b = [int(item) for item in input().split()]
cumsum = [[1] * 410 for _ in range(410)]
for order in range(405):
	for i in range(1, 405):
		cumsum[order][i] = pow(i, order, MOD) + cumsum[order][i - 1]
		cumsum[order][i] %= MOD
dp = [[0] * (m + 1) for _ in range(n + 1)]
dp[0][0] = 1
for i in range(1, n + 1):
	for j in range(0, m + 1):
		for k in range(j + 1):
			l = a[i - 1]
			r = b[i - 1]
			x = (cumsum[j - k][r] - cumsum[j - k][l - 1] + MOD) % MOD
			dp[i][j] += dp[i - 1][k] * x
		dp[i][j] %= MOD
print(dp[-1][-1])


(N, C) = list(map(int, input().split()))
A = list(map(int, input().split()))
B = list(map(int, input().split()))
mod = 10 ** 9 + 7
acc = [[0] for _ in range(401)]
for i in range(401):
	for j in range(1, 401):
		acc[i].append((acc[i][-1] + pow(j, i, mod)) % mod)
dp = [[0 for _ in range(C + 1)] for _ in range(N + 1)]
dp[0][0] = 1
for i in range(N):
	for candy_cur in range(C + 1):
		for candy_plus in range(C - candy_cur + 1):
			dp[i + 1][candy_cur + candy_plus] = (dp[i + 1][candy_cur + candy_plus] + dp[i][candy_cur] * ((acc[candy_plus][B[i]] - acc[candy_plus][A[i] - 1]) % mod) % mod) % mod
print(dp[-1][C])


(N, C) = list(map(int, input().split()))
A = list(map(int, input().split()))
B = list(map(int, input().split()))
MOD = 10 ** 9 + 7
MB = max(B)
Sm = [[1 for _ in range(MB + 1)]]
for c in range(1, C + 1):
	Sm.append([])
	s = Sm[-1]
	sp = Sm[-2]
	for i in range(MB + 1):
		s.append(i * sp[i] % MOD)
for c in range(C + 1):
	s = Sm[c]
	for i in range(1, MB + 1):
		s[i] += s[i - 1]
		s[i] %= MOD
DP = [[0 for _ in range(C + 1)] for _ in range(N + 1)]
DP[0][0] = 1
for n in range(1, N + 1):
	dp = DP[n]
	dpp = DP[n - 1]
	for c in range(C + 1):
		for cc in range(C + 1 - c):
			dp[c + cc] += dpp[c] * (Sm[cc][B[n - 1]] - Sm[cc][A[n - 1] - 1])
			dp[c + cc] %= MOD
print(DP[N][C] % MOD)


def main():
	mod = 10 ** 9 + 7
	(n, c) = map(int, input().split())
	A = list(map(int, input().split()))
	B = list(map(int, input().split()))
	dp = [0] * (c + 1)
	dp[0] = 1
	ans = 0
	p = [[0] * 401 for _ in [0] * 401]
	for i in range(401):
		for j in range(401):
			p[i][j] = pow(j, i, mod)
	for (a, b) in zip(A, B):
		dp2 = [0] * (c + 1)
		q = [0] * (c + 1)
		for i in range(c + 1):
			q[i] = sum(p[i][a:b + 1]) % mod
		for i in range(c + 1):
			temp = 0
			for j in range(i + 1):
				temp += dp[i - j] * q[j]
			dp2[i] = temp % mod
		dp = dp2
	ans += dp[-1]
	print(ans % mod)
main()


(N, C) = map(int, input().split())
A = [int(a) for a in input().split()]
B = [int(a) for a in input().split()]
P = 10 ** 9 + 7
Y = [[pow(i, j, P) for j in range(401)] for i in range(401)]
for i in range(1, 401):
	for j in range(401):
		Y[i][j] = (Y[i][j] + Y[i - 1][j]) % P
X = [[0] * (C + 1) for _ in range(N + 1)]
X[0][0] = 1
for i in range(1, N + 1):
	for j in range(C + 1):
		X[i][j] = sum([X[i - 1][k] * (Y[B[i - 1]][j - k] - Y[A[i - 1] - 1][j - k]) % P for k in range(j + 1)]) % P
print(X[N][C])


import sys
read = sys.stdin.read
readline = sys.stdin.readline
(n, c) = list(map(int, readline().split()))
(*a,) = list(map(int, readline().split()))
(*b,) = list(map(int, readline().split()))
M = 401
MOD = 10 ** 9 + 7
powsum = []
for i in range(M):
	res = [pow(j, i, MOD) for j in range(M)]
	for j in range(1, M):
		res[j] = (res[j] + res[j - 1]) % MOD
	powsum.append(res)
dp = [0] * (c + 1)
dp[0] = 1
for (ai, bi) in zip(a, b):
	ndp = [0] * (c + 1)
	for k in range(c + 1):
		for j in range(k + 1):
			ndp[k] += (powsum[j][bi] - powsum[j][ai - 1]) * dp[k - j] % MOD
		ndp[k] %= MOD
	dp = ndp
print(dp[c] % MOD)


import sys

def MI():
	return list(map(int, sys.stdin.readline().rstrip().split()))

def LI():
	return list(map(int, sys.stdin.readline().rstrip().split()))
(N, C) = MI()
(A, B) = ([0] + LI(), [0] + LI())
mod = 10 ** 9 + 7
X = [[0] * 401 for _ in range(401)]
for k in range(401):
	for l in range(1, 401):
		X[k][l] = X[k][l - 1] + pow(l, k, mod)
		X[k][l] %= mod
dp = [[0] * (C + 1) for _ in range(N + 1)]
dp[0][0] = 1
for i in range(1, N + 1):
	(a, b) = (A[i], B[i])
	for j in range(C + 1):
		x = 0
		for k in range(j + 1):
			x += dp[i - 1][j - k] * (X[k][b] - X[k][a - 1])
			x %= mod
		dp[i][j] = x
print(dp[-1][-1])


import sys
input = sys.stdin.readline
from itertools import accumulate
MOD = 10 ** 9 + 7
(n, c) = map(int, input().split())
A = tuple(map(int, input().split()))
B = tuple(map(int, input().split()))
E = [[0] * (c + 1) for _ in range(n)]
for j in range(c + 1):
	cumsum = tuple((pow(k, j, MOD) for k in range(401)))
	cumsum = tuple((i % MOD for i in accumulate(cumsum)))
	for (i, (a, b)) in enumerate(zip(A, B)):
		E[i][j] = cumsum[b] - cumsum[a - 1]
dp = [[0] * (c + 1) for _ in range(n + 1)]
dp[0][0] = 1
for (i, e) in enumerate(E):
	for (j, f) in enumerate(e):
		for k in range(c + 1):
			if j + k <= c:
				dp[i + 1][j + k] += dp[i][k] * f
				dp[i + 1][j + k] %= MOD
ans = dp[n][c]
print(ans)


import sys
input = sys.stdin.readline
import numpy as np
MOD = 10 ** 9 + 7
(N, C) = map(int, input().split())
A = [int(x) for x in input().split()]
B = [int(x) for x in input().split()]
kth_pow = np.ones((1024, 401), dtype=np.int64)
rng = np.arange(401, dtype=np.int64)
for i in range(1, C + 1):
	kth_pow[i] = kth_pow[i - 1] * rng % MOD
kth_pow_cum = kth_pow.cumsum(axis=1) % MOD
kth_pow_cum[C + 1:] = 0

def convolve(A, B, n=32):
	if n == 8:
		return np.rint(np.fft.irfft(np.fft.rfft(A) * np.fft.rfft(B))).astype(np.int64)
	n //= 2
	M = 1 << n
	A1 = A // M
	A2 = A - M * A1
	B1 = A // M
	B2 = B - M * B1
	X = convolve(A1, B1, n)
	Y = convolve(A1 - A2, B1 - B2, n)
	Z = convolve(A2, B2, n)
	return (X * (M * M % MOD) + (X + Z - Y) * M + Z) % MOD
dp = np.zeros(1024, dtype=np.int64)
dp[0] = 1
for (a, b) in zip(A, B):
	arr = kth_pow_cum[:, b] - kth_pow_cum[:, a - 1]
	dp = convolve(dp, arr)
	dp[C + 1:] = 0
answer = dp[C]
print(answer)


(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)
		ru[cnt][x + 1] %= 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])


import os
import sys
if os.getenv('LOCAL'):
	sys.stdin = open('_in.txt', 'r')
sys.setrecursionlimit(2147483647)
INF = float('inf')
IINF = 10 ** 18
MOD = 10 ** 9 + 7

def ModInt(mod):

	class _ModInt:

		def __init__(self, value):
			self.value = value % mod

		def __add__(self, other):
			if isinstance(other, _ModInt):
				return _ModInt(self.value + other.value)
			else:
				return _ModInt(self.value + other)

		def __sub__(self, other):
			if isinstance(other, _ModInt):
				return _ModInt(self.value - other.value)
			else:
				return _ModInt(self.value - other)

		def __radd__(self, other):
			return self.__add__(other)

		def __mul__(self, other):
			if isinstance(other, _ModInt):
				return _ModInt(self.value * other.value)
			else:
				return _ModInt(self.value * other)

		def __truediv__(self, other):
			raise NotImplementedError()

		def __repr__(self):
			return str(self.value)
	return _ModInt
MI = ModInt(MOD)
(N, C) = list(map(int, sys.stdin.readline().split()))
A = list(map(int, sys.stdin.readline().split()))
B = list(map(int, sys.stdin.readline().split()))

def solve():
	P = [[1] * (C + 1) for _ in range(max(B) + 1)]
	P[0] = [MI(0)] * (C + 1)
	for i in range(1, len(P)):
		for c in range(1, C + 1):
			P[i][c] = P[i][c - 1] * i
	cs = [[0] * (C + 1) for _ in range(max(B) + 1)]
	for c in range(C + 1):
		s = 0
		for i in range(len(P)):
			s += P[i][c]
			cs[i][c] = s
	S = [[0] * (C + 1) for _ in range(N)]
	for i in range(N):
		for c in range(C + 1):
			S[i][c] = cs[B[i]][c] - cs[A[i] - 1][c]
	dp = S[0][:]
	for i in range(1, N):
		for c in reversed(list(range(C + 1))):
			s = 0
			for j in range(c + 1):
				s += dp[c - j] * S[i][j]
			dp[c] = s
	return dp[-1]
print(solve())


from itertools import accumulate
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
mod = 10 ** 9 + 7
X = [list(accumulate([pow(x, d, mod) for x in range(401)])) for d in range(C + 1)]
dp = [[0] * (C + 1) for _ in range(N + 1)]
dp[0][0] = 1
for i in range(1, N + 1):
	for d in range(C + 1):
		dp[i][d] = sum([dp[i - 1][d - k] * (X[k][B[i - 1]] - X[k][A[i - 1] - 1]) for k in range(d + 1)]) % mod
print(dp[-1][-1])


import sys
input = sys.stdin.readline
mod = 10 ** 9 + 7
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
dp = [0] * (C + 1)
dp[0] = 1
for i in range(N):
	X = [0] * (C + 1)
	for j in range(A[i], B[i] + 1):
		x = 1
		for k in range(C + 1):
			X[k] = (X[k] + x) % mod
			x = x * j % mod
	ndp = [0] * (C + 1)
	for j in range(C + 1):
		for k in range(C + 1 - j):
			ndp[j + k] = (ndp[j + k] + dp[j] * X[k]) % mod
	dp = ndp
print(dp[C])


MOD = 10 ** 9 + 7
tab = []
for i in range(401):
	now = []
	cnt = 0
	for q in range(401):
		cnt += pow(q, i, MOD)
		now.append(cnt)
	tab.append(now[:])
(n, c) = map(int, input().split())
A = [int(i) for i in input().split()]
B = [int(i) for i in input().split()]
enji = []
for i in range(n):
	now = []
	for q in range(c + 1):
		now.append(tab[q][B[i]] - tab[q][A[i] - 1])
	enji.append(now[:])
dp = [0 for i in range(c + 1)]
dp[0] = 1
ndp = [0 for i in range(c + 1)]
for i in range(n):
	for step in range(c + 1):
		val = enji[i][step] % MOD
		for fr in range(c + 1 - step):
			ndp[fr + step] += dp[fr] * val % MOD
			ndp[fr + step] %= MOD
	dp = ndp[:]
	ndp = [0 for i in range(c + 1)]
print(dp[-1])


from itertools import accumulate
mod = 10 ** 9 + 7
(N, C) = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
memo = []
for p in range(C + 1):
	tmp = [pow(i, p, mod) for i in range(401)]
	memo.append(tuple(accumulate(tmp)))
dp = [[0] * (C + 1) for _ in range(N + 1)]
dp[0][0] = 1
for (i, (a, b)) in enumerate(zip(A, B)):
	for j in range(C + 1):
		for k in range(j + 1):
			dp[i + 1][j] += dp[i][k] * (memo[j - k][b] - memo[j - k][a - 1])
			dp[i + 1][j] %= mod
print(dp[N][C])


(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):
			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])


import sys
input = sys.stdin.buffer.readline
(N, C) = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
c = [0] * (N * (C + 1))
mod = 10 ** 9 + 7
for i in range(N):
	c[i * (C + 1)] = b[i] - a[i] + 1
for i in range(N):
	for k in range(a[i], b[i] + 1):
		t = 1
		for j in range(C):
			t *= k
			t %= mod
			c[i * (C + 1) + j + 1] += t
			c[i * (C + 1) + j + 1] %= mod
dpx = [0] * (C + 1)
dpy = [0] * (C + 1)
dpx[0] = 1
for i in range(N):
	if i % 2:
		dpx = [0] * (C + 1)
	else:
		dpy = [0] * (C + 1)
	for j in range(C + 1):
		for k in range(j, C + 1):
			if i % 2:
				dpx[k] += dpy[j] * c[i * (C + 1) + k - j]
				dpx[k] %= mod
			else:
				dpy[k] += dpx[j] * c[i * (C + 1) + k - j]
				dpy[k] %= mod
if N % 2:
	print(dpy[-1] % mod)
else:
	print(dpx[-1] % mod)


def main1(n, c, a, b):
	mod = 10 ** 9 + 7
	dp = [[0] * (c + 1) for i in range(n + 1)]
	dp[0][0] = 1
	for i in range(n):
		ary = [0] * (b[i] + 1 - a[i])
		tmp = 0
		for j in range(c + 1):
			tmp += dp[i][j] * (b[i] + 1 - a[i])
			tmp %= mod
			dp[i + 1][j] += tmp
			dp[i + 1][j] %= mod
			tmp = 0
			for k in range(b[i] + 1 - a[i]):
				ary[k] += dp[i][j]
				ary[k] *= a[i] + k
				ary[k] %= mod
				tmp += ary[k]
				tmp %= mod
	return dp[n][c]

def __starting_point():
	(n, c) = map(int, input().split())
	a = list(map(int, input().split()))
	b = list(map(int, input().split()))
	print(main1(n, c, a, b))
__starting_point()