#include<iostream>
#include<vector>
#include<cmath>
#include<fstream>
using namespace std;
ifstream fin("double_muscle.in");
ofstream fout("double_muscle.out");
struct node{
    int x,y;
    node(){}
    node(int a,int b)
    {
        x=a,y=b;
    }
};
vector <node> v;
int n,m,ans=1<<10,x,y,a[100005],maxx;
int main()
{
    fin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        fin>>x>>y;
        maxx=maxx>x?maxx:x;
        v.push_back(node(x,y));
    }
    for(int i=0;i<v.size();i++)
        for(int j=i+1;j<v.size();j++)
        {
            if(abs(v[i].y-v[j].y)-1>=m) 
                ans=min(ans,abs(v[i].x-v[j].x));
        }
    fout<<ans<<endl;
    return 0;
}