/* -*- coding: utf-8 -*-
 *
 * 2694.cc:  No.2694 The Early Bird Catches The Worm - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], bs[MAX_N];
ll ass[MAX_N + 1], bss[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n, h;
  scanf("%d%d", &n, &h);
  for (int i = 0; i < n; i++) scanf("%d", as + i);
  for (int i = 0; i < n; i++) scanf("%d", bs + i);

  for (int i = 0; i < n; i++) ass[i + 1] = ass[i] + as[i];
  for (int i = 0; i < n; i++) bss[i + 1] = bss[i] + bs[i];

  ll maxx = 0, y = 0;
  for (int i = 0, j = 0; j < n; i++) {
    while (j < n && y + (ll)bs[j] * (j + 1 - i) <= h) {
      y += (ll)bs[j] * (j + 1 - i);
      j++;
    }

    maxx = max(maxx, ass[j] - ass[i]);
    //printf(" %d,%d: x=%lld, y=%lld\n", i, j, ass[j] - ass[i], y);

    y -= bss[j] - bss[i];
  }

  printf("%lld\n", maxx);
  
  return 0;
}