#include<fstream>

using namespace std;

ifstream cin("energii.in");
ofstream cout("energii.out");

typedef struct lol{
	int e,c;
}troll;

troll a[1005][1005];
int g,w,eg[1005],cg[1005];

main(void)
{
	cin>>g>>w;
	for(int i=1;i<=g;++i)cin>>eg[i]>>cg[i];
	for(int i=1;i<=g;++i)
		for(int j=1;j<=g;++j){
		if(i==j){
			if(eg[i]>=w)a[i][j].e=eg[i],a[i][j].c=cg[i];
		}
		else{
			if(eg[i]+eg[j]>=w)a[i][j].e=eg[i]+eg[j],a[i][j].c=cg[i]+cg[j];
		}
		}
	int mn=10005;
	for(int i=1;i<=g;++i)
		for(int j=1;j<=g;++j)if(a[i][j].c<mn && a[i][j].c>0)mn=a[i][j].c;
	if(mn==10005)cout<<-1;
	else cout<<mn;
}