#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int main() {
    int g, w, eg, cg, costMin = 1002, el = 0;
    fin >> g >> w;
    for(int i = 0; i < g; i++){
        fin >> eg >> cg;
        if(eg >= w){
            if(cg < costMin){
                costMin = cg;
                el++;
            }
        }
    }
    if(el > 0){
        fout << costMin;
    }
    else{
        fout << -1;
    }

    return 0;
}