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C - Big Array

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.

3 4
1 1
2 2
3 3

3

The resulting array is the same as the one in the problem statement.

10 500000
1 100000
1 100000
1 100000
1 100000
1 100000
100000 100000
100000 100000
100000 100000
100000 100000
100000 100000

1