N,H=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
ans=0
R=0
cumA=0
cumB=0
resB=0
for L in range(N):
  while R!=N:
    ncumA=cumA+A[R]
    ncumB=cumB+B[R]*(R-L+1)
    nresB=resB+B[R]
    if ncumB<=H:
      R+=1
      cumA=ncumA
      cumB=ncumB
      resB=nresB
    else:
      break
  ans=max(ans,cumA)
  cumA-=A[L]
  cumB-=resB
  resB-=B[L]
print(ans)