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 (2.7.1) (judge verdict: Accepted)

n,k = gets.strip.split.map(&:to_i)
rec = Array.new(10**5,0)
n.times do
  a,b = gets.strip.split.map(&:to_i)
  rec[a-1] += b
end

s = Array.new(rec.length+1)
s[0] = 0
0.upto(rec.length-1) do |i|
  s[i+1] = s[i] + rec[i]
end

i = 0
while s[i] < k do
  i += 1
end
puts i