#include <fstream>

using namespace std;

ifstream cin ("energii.in");
ofstream cout ("energii.out");

int g, w;

int main() {
    cin >> g >> w;
    int cost_minim = 1e9;
    for (int i = 1; i <= g; i++) {
        int eg, cg;
        cin >> eg >> cg;
        if (eg >= w && cg < cost_minim)
            cost_minim = cg;
    }
    if (cost_minim == 1e9)
        cost_minim = -1;
    cout << cost_minim << "\n";
    return 0;
}