#include<stdio.h>
FILE *f=fopen("energii.in","r");
FILE *h=fopen("energii.out","w");
int g,w,i,eg[101],cg[101],j,cmin,maxi;
void citire()
{
	fscanf(f,"%d",&g);
	fscanf(f,"%d",&w);
	for(i=1;i<=g;i++)
		for(j=1;j<=g;j++)
	{
	fscanf(f,"%d %d", &eg[i] , &cg[i]);
	}
	fclose(f);
}
int main()
{
	citire();
	maxi=0;
	for(i=1;i<=g;i++)
	{
	if(maxi<=cg[i]) 
		maxi=cg[i];
	}
	if(maxi>=w) fprintf(h,"%d",maxi);
	fclose(h);
	return 0;
}