#include<bits/stdc++.h>
using namespace std;
struct node{
	int x,y;
}e[200000];
bool cmp(node a,node b)
{
	return a.y<b.y;
}
int main(){
	int n,m,ans=0x3f3f3f3f;
	freopen("double_muscle.in","r",stdin);
	freopen("double_muscle.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=n;i++)
		cin>>e[i].x>>e[i].y;
	sort(e+1,e+n+1,cmp);
	for(int i=1;i<=n;i++)
		for(int j=i+1;j<=n;j++)
			if(e[j].y-e[i].y>=m)
				ans=min(ans,abs(e[i].x-e[j].x));
	cout<<ans<<endl;
	return 0;
}