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 (3.8.2) (judge verdict: Accepted)

N,K=map(int,input().split())

#S = [[0 for j in range(3)] for i in range(2)]　2行3列の場合
S = [[0 for j in range(2)] for i in range(100010)]

for i in range(N):
    T=list(map(int,input().split()))
    S[T[0]][0]=T[0]
    S[T[0]][1]+=T[1]

#print(S)

for i in range(100010):
    if S[i][0]!=0:
        K-=S[i][1]
        if K<=0:
            print(S[i][0])
            exit()