input_line = gets.chomp!.split(' ').map{|n| n.to_i}
v_line = []
for i in 1..input_line[0]
        input_line2 = gets.chomp!.split(' ').map{|n| n.to_i}
        if input_line2[1] <= input_line[1] then
                v_line.push(input_line2[0])
        end
end
if v_line == [] then
        puts -1
end
puts v_line.max