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)

def big_array(N: int, K: int, queries: list)->int:
    d = {}
    for a, b in queries:
        d.setdefault(a, 0)
        d[a] += b

    count = 0
    ans = 0
    for k, v in sorted(d.items()):
        count += v
        if K <= count:
            ans = k
            break
    return ans


if __name__ == "__main__":
    N = 0
    N, K = map(int, input().split())
    queries = [tuple(map(int, input().split())) for _ in range(N)]
    ans = big_array(N, K, queries)
    print(ans)