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)

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

arr_num, arr_times = [], []

for i in range(N) :
    a, b = map(int, input().split())
    
    arr_num.append(a)
    arr_times.append(b)
    
# do sort 
s_num, s_times = [], []
s_idx = sorted(range(N), key = lambda k : arr_num[k])

# propagate arr 
for i in s_idx :
    s_num.append(arr_num[i])
    s_times.append(arr_times[i])

cur_idx = 0

for i in range(N) :
    if cur_idx <= K :
        cur_idx += s_times[i]
        
    if cur_idx >= K :
        print(s_num[i])
        break