#include <stdio.h>
#include <stdlib.h>
#include <math.h>

typedef struct {
    int g;
    int x;
} Node;

int CmpNode(const void *a, const void *b) {
    Node *an = (Node *)a;
    Node *bn = (Node *)b;
    return an->x - bn->x;
}

int main() {
    int n, k;
    scanf("%d %d", &n, &k);
    Node *list = (Node *)calloc(n, sizeof(Node));
    for (int i = 0; i < n; i++) {
        scanf("%d %d", &list[i].g, &list[i].x);
    }
    qsort(list, n, sizeof(Node), CmpNode);
    int ans = 0;
    int temp = 0;
    for(int l = 0, r = 0; r <= n; r++) {
        temp += list[r].g;
        while (list[r].x - list[l].x > 2 * k) {
            temp -= list[l++].g;
        }
        ans = fmax(ans, temp);
    }

    printf("%d", ans);
    return 0;
}