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: Wrong Answer)

n, k = gets.chomp.split.map(&:to_i)
num = Hash.new{|hash,key| hash[key] = 0}
temp_sum = 0
temp_max = false
n.times do
    a, b = gets.chomp.split.map(&:to_i)
    if temp_max
        next if a >= temp_max
    else
        temp_sum += b
        temp_max = a if temp_sum >= k
    end
    num[a] += b
end
answer = num.sort
p num
p answer
sum = 0
answer.each do |i|
    sum += i[1]
    if sum >= k
        puts i[0]
        break
    end
end