#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int n,w,e[10005],c[10005];
void sortare(int a[],int b[],int n)
{int aux,i,j;
    for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
    if(e[i]>e[j]){
        aux=e[i];
        e[i]=e[j];
        e[j]=aux;
        aux=c[i];
        c[i]=c[j];
        c[j]=aux;
    }
}
int main()
{
   fin>>n>>w;
   for(int i=1;i<=n;i++)
   {
       fin>>e[i]>>c[i];
   }
  sortare(e,c,n);
   int mini=c[n];
   if(e[n]<w)fout<<-1;
   else
   {for(int i=1;i<=n;i++)
    if(e[i]>w&&c[i]<mini)mini=c[i];
   fout<<mini;}

}