#include<iostream>
#include<algorithm>
#include<set>

using namespace std;

const int N=200010;
typedef pair<int,int> PII;

PII banks[N];

int main()
{
    int n,min_dist;
    cin>>n>>min_dist;
    for(int i=1;i<=n;i++) cin>>banks[i].first>>banks[i].second;

    sort(banks+1,banks+1+n);

    int res=0;
    for(int j=0,i=1,maxv=0;i<=n;i++ )
    {
        while(j+1<i && banks[i].first-banks[j+1].first>=min_dist)
        {
            j++;
            maxv=max(maxv,banks[j].second);
        }
        res=max(res,banks[i].second+maxv);
    }    

    cout<<res<<endl;


    return 0;
}