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: Wrong Answer)

def f():
    n, k = map(int, input().split())

    d = {}
    key_list = []

    for _ in range(n):
        a, b = map(int, input().split())
        if a in d.keys():
            d[a] += b
        else:
            d[a] = b

        key_list.append(a)

    key_list = sorted(key_list)

    curr_num = 0
    for key in key_list:
        curr_num += d[key]
        if curr_num >= k:
            print(key)
            return


if __name__ == "__main__":
    f()