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 Common Lisp (SBCL 1.1.14) (judge verdict: Wrong Answer)

(defun solver ()
  (let* ((N (read)) (K (read))
        (array-a (make-array N :fill-pointer 0))
        (array-b (make-array N :fill-pointer 0)))
    (do ((i 0 (incf i))) ((= i N))
        (vector-push (read) array-a)
        (vector-push (read) array-b))
    (let ((count 0))
    (do ((j 0 (incf j))) ((= j N))
        (incf count (aref array-b j))
        (when (>= count K)
          (return (format t "~A~%" (aref array-a j))))))))

(solver)