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: Runtime Error)

n_k = gets().split(" ")
n = n_k[0].to_i
k = n_k[1].to_i

a = Array.new(n)
b = Array.new(n)

for i in 0..n-1
	str = gets().split(" ")
	a[i] = str[0].to_i
	b[i] = str[1].to_i
end

count = 0

for j in 0..n-1
	count = count + b[j]
end

c = Array.new(count)

time = 0

for t in 0..n-1
	for u in 0..b[t]-1
		c[time]=a[t]
		time = time + 1
	end
end

d = c.sort

puts c
puts d[k-1]