//11/10/2007 15:40 -  16:04
//energii

#include <fstream>

using namespace std;
#define FIN "t01energii.in"
#define FOUT "t01energii.out"

int g,w,eg,cg,cgmin = -1 ,ok;

void main()
{
	ifstream fin(FIN);
	ofstream fout(FOUT);
	fin >> g >> w;
	for(int i = 0; i < g; ++i){
		
		fin >> eg >> cg;
		if (eg < w && i == g-1 && cgmin == -1)
			fout << -1;
		else
			if( eg < w )
				continue;
			else 
				if( eg >= w )
					if(!ok) 
						cgmin = cg,ok = 1;
					else
						if(cg < cgmin)
							cgmin = cg;
	}
	fout << cgmin;
}