import sys, math
sys.setrecursionlimit(10**8)
sys.set_int_max_str_digits(0)
INF = 1e18
MOD = 998244353
from bisect import bisect_left, bisect_right
from collections import deque, defaultdict, Counter
from itertools import product, combinations, permutations, groupby, accumulate
from heapq import heapify, heappop, heappush
input = sys.stdin.readline
def I():   return input().rstrip()
def II():  return int(input().rstrip())
def IS():  return input().rstrip().split()
def MII(): return map(int, input().rstrip().split())
def LI():  return list(input().rstrip())
def TII(): return tuple(map(int, input().rstrip().split()))
def LII(): return list(map(int, input().rstrip().split()))
def LSI(): return list(map(str, input().rstrip().split()))
def GMI(): return list(map(lambda x: int(x) - 1, input().rstrip().split()))
def kiriage(a, b): return (a+b-1)//b

N, H = MII()
A = LII()
B = LII()
rB = list(accumulate(B, initial=0))
que = deque()
L = 0
ans = 0
satisfaction = 0
fatigue = 0

for i in range(N):
    a, b = A[i], B[i]
    
    # とりあえず append する
    que.append(i)
    fatigue += (L + 1)*b
    L += 1
    satisfaction += a

    # H以下になるように調整
    while fatigue > H:
        l = que[0]
        r = que[-1]
        fatigue -= rB[r + 1] - rB[l]
        satisfaction -= A[l]
        que.popleft()
        L -= 1
            
    # i追加時の最善状態にできた
    #print(i, que)
    if satisfaction > ans:
        ans = satisfaction

print(ans)