import java.util.Scanner;
class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int H = sc.nextInt();
		int[] A = new int[N];
		for(int i=0;i<N;i++)
			A[i] = sc.nextInt();
		long[] sumA = new long[N+1];
		for(int i=0;i<N;i++)
			sumA[i+1] = sumA[i]+A[i];
		long[] B = new long[N];
		for(int i=0;i<N;i++)
			B[i] = sc.nextInt();
		long[] sumB = new long[N+1];
		for(int i=0;i<N;i++)
			sumB[i+1] = sumB[i]+B[i];
		long ans = 0;
		long now = 0;
		int r = 0;
		for(int l=0;l<N;l++){
			if(B[l]>H)
				continue;
			while(r<N&&now+B[r]*(r-l+1)<=H){
				now += B[r]*(r-l+1);
				r++;
			}
			ans = Math.max(ans,sumA[r]-sumA[l]);
			now -= sumB[r]-sumB[l];
		}
		System.out.println(ans);
	}
}