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)

# 空の配列が 1 つあります。
# この配列に、整数を配列に挿入する操作を N 回行います。
# i(1≦i≦N) 回目の操作では、配列に整数 ai を bi 個挿入します。
# N 回の挿入操作後の配列の中で、K 番目に小さい数を求めてください。
# 例えば、配列が 
# {1,2,2,3,3,3} の時、4 番目に小さい数は 3 となります。

# 操作の回数と求めたい数の番号を取得
input_line_1 = gets.chomp.split
n = input_line_1[0].to_i
k = input_line_1[1].to_i

the_array = Array.new(100001, 0)

# 配列に、与えられた整数を挿入
n.times do
  # 2つの整数を取得
  input = gets.chomp.split
  a = input[0].to_i
  b = input[1].to_i

  the_array[a] += b
end

(1..100000).each do |i|
  k -= the_array[i]
  if k <= 0
    puts i
    break
  end
end