单调队列+二分答案
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
struct Node{
int x, y;
}nd[100005];
int n, d, ans, q1[100005], q2[100005], l1, r1, l2, r2;
bool cmp(Node u, Node v){
return u.x<v.x;
}
bool check(int lim){
l1 = 1, r1 = 0;
l2 = 1, r2 = 0;
for(int i=1; i<=n; i++){
while(l1<=r1 && nd[q1[l1]].x<nd[i].x-lim) l1++;
while(l1<=r1 && nd[q1[r1]].y>nd[i].y) r1--;
q1[++r1] = i;
while(l2<=r2 && nd[q2[l2]].x<nd[i].x-lim) l2++;
while(l2<=r2 && nd[q2[r2]].y<nd[i].y) r2--;
q2[++r2] = i;
if(nd[q2[l2]].y-nd[q1[l1]].y>=d) return true;
}
return false;
}
int main(){
cin>>n>>d;
for(int i=1; i<=n; i++)
scanf("%d %d", &nd[i].x, &nd[i].y);
sort(nd+1, nd+1+n, cmp);
int l=0, r=nd[n].x-nd[1].x, mid;
while(l<=r){
mid = (l + r) >> 1;
if(check(mid)){
ans = mid;
r = mid - 1;
}
else l = mid + 1;
}
if(ans==0) cout<<"-1"<<endl;
else cout<<ans<<endl;
return 0;
}