代码如下：

#include <bits/stdc++.h>
using namespace std;

const int NR = 1e5 + 10;
struct water
{
	int x, t, id;
	bool operator < (const water &o) const
	{
		return x < o.x;
	}
} a[NR];

int n, d;
deque<int> q;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	
	cin >> n >> d;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i].x >> a[i].t;
		a[i].id = i;
	}
	sort(a + 1, a + n + 1);
	
	int l = 1, r = 1, ans = 2e9;
	q.push_front(1);
	while (true)
	{
		while (!q.empty() && a[q.back()].t - a[q.front()].t >= d)
		{
			ans = min(ans, a[q.front()].x - a[q.back()].x);
			l++;
			while (!q.empty() && q.back() < l)
			{
				// cout << "Water[" << a[q.back()].id << "] is poped out." << endl;
				q.pop_back();
			}
		}
		
		if (r >= n) break;
		
		bool flag = true;
		while (q.empty() || a[q.back()].t - a[q.front()].t < d)
		{
			if (r >= n) break;
			r++;
			while (!q.empty() && a[r].t > a[q.front()].t)
			{
				// cout << "Water[" << a[q.front()].id << "] is poped out." << endl;
				q.pop_front();
			}
			q.push_front(r);
			// cout << "Water[" << a[q.front()].id << "] is pushed in." << endl;
		}
		
		if (r < n) ans = min(ans, a[r].x - a[l].x);
	}
	
	if (ans >= 1e9) cout << -1 << endl;
	else cout << ans << endl;
	return 0;
}