#include<cstdio>
#include<cstring>
using namespace std;
struct databox
{
	long long x;
	int i;
}x[600010],y[600010];
inline void qsort1(int l,int r)
{
	register int i=l,j=r;register databox mid=x[(l+r)/2],t;
	while(i<=j){
		while(x[i].x<mid.x) i++;
		while(x[j].x>mid.x) j--;
		if(i<=j){
			t=x[i];
			x[i]=x[j];
			x[j]=t;
			i++;j--;
		}
	}
	if(l<j) qsort1(l,j);
	if(i<r) qsort1(i,r);
}
inline void qsort2(int l,int r)
{
	register int i=l,j=r;register databox mid=y[(l+r)/2],t;
	while(i<=j){
		while(y[i].x<mid.x) i++;
		while(y[j].x>mid.x) j--;
		if(i<=j){
			t=y[i];
			y[i]=y[j];
			y[j]=t;
			i++;j--;
		}
	}
	if(l<j) qsort2(l,j);
	if(i<r) qsort2(i,r);
}
int main()
{
	register int n;
	register long long d;
	register int i;
	register long long nowans=0,ans=0,nxsum=0,nysum=0,nx,ny;
	scanf("%d%lld",&n,&d);
	for(i=1;i<=n;i++){
		scanf("%lld%lld",&x[i].x,&y[i].x);
		x[i].i=i,y[i].i=i;
	}
	qsort1(1,n);
	qsort2(1,n);
	for(i=1;i<=n;i++){
		nxsum+=x[i].x;
		nysum+=y[i].x;
		nowans+=i*x[i].x-nxsum;
		nowans+=i*y[i].x-nysum;
	}
	if(nowans<=d){
		printf("-1\n");return 0;
	}
	register int l=1,r=n,mid;
	while(l<r)
	{
		mid=(l+r)/2;nxsum=0,nysum=0;
		nx=ny=0;nowans=0;
		for(i=1;i<=n;i++){
			if(x[i].i<=mid){
				nx++;nxsum+=x[i].x;
				nowans+=x[i].x*nx-nxsum;
			}
			if(y[i].i<=mid){
				ny++;nysum+=y[i].x;
				nowans+=y[i].x*ny-nysum;
			}
		}
		if(nowans<=d) l=mid+1;
		else r=mid;
	}
	printf("%d\n",l);
	return 0;
}