import sys
input = sys.stdin.readline

N,H=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

S=[0]
for a in A:
    S.append(S[-1]+a)
    
T=[0]
for a in B:
    T.append(T[-1]+a)

ind=0
now=0
ANS=0
for i in range(N):
    ind=max(ind,i)

    while ind<N:
        if now+B[ind]*(ind-i+1)<=H:
            now+=B[ind]*(ind-i+1)
            ind+=1
        else:
            break

    #print(ind)

    ANS=max(ANS,S[ind]-S[i])
    now-=T[ind]-T[i]

print(ANS)