#include <fstream>
using namespace std;
int a,b,c,d,i;
int main () {
	ifstream f("energii.in");
	ofstream g("energii.out");
	f>>a;
	f>>b;
	int max;
	for(i=1;i<=a;i++) {
		f>>c>>d;
		if (c>=b && d<max ) max=d; }
	if (max == 0) g<<-1;
		else g<<max;
		f.close();
		g.close();
		return 0;
}