Problem:
Score : 300 points

Problem Statement

There is an empty array.
The following N operations will be performed to insert integers into the array.
In the i-th operation (1≤i≤N), b_i copies of an integer a_i are inserted into the array.
Find the K-th smallest integer in the array after the N operations.
For example, the 4-th smallest integer in the array \{1,2,2,3,3,3\} is 3.

Constraints

1≤N≤10^5

1≤a_i,b_i≤10^5

1≤K≤b_1…+…b_n

All input values are integers.

Input

Input is given from Standard Input in the following format:

N K
a_1 b_1
:
a_N b_N

Output

Print the K-th smallest integer in the array after the N operations.

Sample Input 1

3 4
1 1
2 2
3 3

Sample Output 1

3

The resulting array is the same as the one in the problem statement.

Sample Input 2

10 500000
1 100000
1 100000
1 100000
1 100000
1 100000
100000 100000
100000 100000
100000 100000
100000 100000
100000 100000

Sample Output 2

1

Solution in Ruby (2.3.3) (judge verdict: Accepted)

line = gets
data = line.split(" ")
n = data[0].to_i
k = data[1].to_i
bi = Hash.new
n.times do |i|
  line = gets
  data = line.split(" ")
  a = data[0].to_i
  if bi[a] == nil
    bi[a] = data[1].to_i
  else
    bi[a] += data[1].to_i
  end
end
ai = bi.keys
ai.sort!
ai.each do |a|
  k -= bi[a]
  if k <= 0
    puts a
    break
  end
end