#include <fstream>
using namespace std;

ifstream is("energii.in");
ofstream os("energii.out");

int main()
{
    int G, W, EGi, CGi, cmin = 10001;
    is >> G;
    is >> W;
    bool ok;
    for( int i = 0; i < G; ++i )
    {
        is >> EGi;
        is >> CGi;
        if ( EGi >= W )
        {
            ok = true;
            if( CGi < cmin )
                cmin = CGi;
        }
    }

    if( ok == true )
        os << cmin;
    else
        os << -1;
    is.close();
    os.close();
    return 0;
}