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 Python (3.4.3) (judge verdict: Accepted)

# -*- coding:utf-8 -*-

""" 方針
[入力例１]
3 4
1 1
2 2
3 3

ans = [1, 2, 2, 3, 3, 3]
K=4より、答えは3


"""

def solve():
    N, K = list(map(int, input().split()))
    A, B = [], []

    num_cnt_hash = {}
    for i in range(N):
        a, b = list(map(int, input().split()))

        if not a in num_cnt_hash:
            num_cnt_hash[a] = 0
        num_cnt_hash[a] += b
    
    nums = list(num_cnt_hash.keys())
    nums.sort()

    k = 0
    for num in nums:
        k += num_cnt_hash[num]
        if k >= K:
            print(num)
            return


if __name__ == "__main__":
    solve()