#include<bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
int n,d;
struct node{
	double x,y;
}a[1000005];
bool cmp(node l,node r){
	return l.y<r.y;
}
int ma=-1e9,ans;
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>d;
	for(int i=1;i<=n;i++){
		int x1,y1;
		cin>>x1>>y1;
		if(y1>d){
			cout<<-1;
			return 0;
		}
		a[i].x=x1-sqrt(d*d-y1*y1);
		a[i].y=x1+sqrt(d*d-y1*y1);
	}
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++){
		if(a[i].x>ma){
			ma=a[i].y;
			ans++;
		}
	}cout<<ans;
	return 0;
}

#include<bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
bool vis[1000005];
struct node{
	int b,e,t;
}a[1000005];
bool cmp(node x,node y){
	return x.e<y.e;
}
int n,m,ans;
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		cin>>a[i].b>>a[i].e>>a[i].t;
	}
	sort(a+1,a+m+1,cmp);
	for(int i=1;i<=m;i++){
		int top=0;
		for(int j=a[i].b;j<=a[i].e;j++){
			if(vis[j]==1)top++;
		}
		if(top>=a[i].t)continue;
		for(int j=a[i].e;j>=a[i].b;j--){
			if(vis[j]==0){
				vis[j]=1;
				ans++,top++;
				if(top==a[i].t)break;
			}
		}
	}cout<<ans;
	return 0;
}