#include <fstream>
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");
int n,G,a,b,minim=10002,minim2=10002;
bool ok,ok2;
int main()
{
    cin>>n>>G;
    for(int i=1; i<=n; i++)
    {
        cin>>a>>b;
        if(a==G)
        {
            if(b<minim)
                minim=b;
            ok=1;
        }
        if(a>G)
        {
            if(b<minim2)
                minim2=b;
            ok2=1;
        }

    }
    if(ok)
        cout<<minim;
    if(!ok && ok2)
        cout<<minim2;
    if(!ok && !ok2)
        cout<<-1;
}