using namespace std;
#include <fstream>
#include <iostream>
int main()
{
ifstream in ("energii.in");
ofstream out ("energii.out");
struct generator {int EGi, CGi;};
       generator g[1001], min;
int G,W,i;
in>>G>>W;
min.EGi=W; min.CGi=10000;
for (i=1;i<=G;i++)
     {in>>g[i].EGi>>g[i].CGi;}
for (i=1;i<=G;i++)
     if(g[i].EGi>=min.EGi)
		 if(g[i].CGi<=min.CGi)
			 min=g[i];
if((min.EGi==W)&&(min.CGi==10000)) out<<-1;
  else out<<min.CGi;
return 0;
}