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)

n, k = gets.chomp.split.map(&:to_i)
ki = 0
# k番目に小さい数...?
# ->ソートしたときの順番だと思われ
arr = {}
n.times do
  a, b = gets.chomp.split.map(&:to_i)
  if arr[a].nil?
    arr[a] = b
  else
    arr[a]+=b
  end
end
arr = arr.sort_by{|x|x[0]} # 頭湧いてるからarr[0]にしてた
arr.each do |a, v|
  if ki+v<k
    ki+=v
  else
    puts a
    exit  # 頭湧いてるからbreakにしてた
  end
end