#include <bits/stdc++.h>
#include <math.h>
//define
#define yes (cout<<"Yes"<<endl)
#define no (cout<<"No"<<endl)
using namespace std;

int main(){
int n,k;cin>>n>>k;
vector<int> a(n),b(n);
for(int i=0;i<n;i++)cin>>a[i]>>b[i];
int ans=0;
for(int i=0;i<n;i++){
    if(b[i]<=k)ans=max(ans,a[i]);
}
if(ans)cout<<ans<<endl;
else cout<<-1<<endl;
}