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 (2.7.6) (judge verdict: Accepted)

#!/usr/bin/env python

N,K=map(int,raw_input().split())
arr=[[0,0]]*N
for i in range(N):
    arr[i]=map(int,raw_input().split())
#print "Not sorted arr",
#print arr
arr=sorted(arr)
#print "sorted",
#print arr
sum=0
for i in range(N):
#    print "i: "+str(i)
    sum=sum+arr[i][1]
#    print "sum = "+str(sum)
    if sum>=K:
#        print "sum: "+str(sum)
        print arr[i][0]
        break