#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
int n ,d;
const int N = 1e6+ 10;
typedef pair<int, int> PII;
#define x first
#define y second
PII a[N];
int res;
int main(){
    cin >> n >> d;
    for (int i = 1; i <= n; i ++ ){
        cin >> a[i].x >> a[i].y;
    }
    sort(a + 1, a + n + 1);int mx = -1e9;//必须让 mx+a[i].y<=0，所以mx直接初始化很小的数
    for (int i = 1, j = 0; i <= n; i ++){
        while (j + 1 < i && a[i].x - a[j+1].x >= d){
            mx = max(mx, a[++j].y);
        }
        res = max(res, mx + a[i].y);
    }
    cout << res << '\n';
    return 0;
}