#include <iostream>
#include<fstream>
#include <algorithm>
using namespace std;
ifstream fin ("energii.in");
ofstream fout ("energii.out");
int main()
{
   int a,b,c,g1,g2,v[1005],j=1,i,min1=5002;
   fin>>a>>b;
   for(i=1;i<=a;i++)
   {

      fin>>g1>>g2;
      if(g1>=b)
      {
          if(g2<min1)
          min1=g2;



      }
   }

   if(min1<5002)
fout<<min1;
else
    fout<<"-1";


}