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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func splitInt(str string, sep string) (nums []int) {
	sp := strings.Split(str, sep)
	nums = make([]int, len(sp))
	for i, s := range sp {
		n, _ := strconv.Atoi(s)
		nums[i] = n
	}
	return
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Scan()

	nm := splitInt(sc.Text(), " ")

	sorted := make([][]int, 0, nm[0])
	for i := 0; i < nm[0]; i++ {
		sc.Scan()
		sorted = append(sorted, splitInt(sc.Text(), " "))
	}

	for i := 0; i < len(sorted); i++ {
		for j := i + 1; j < len(sorted); j++ {
			if sorted[i][0] >= sorted[j][0] {
				sorted[i][0] = sorted[j][0]
			}
		}
	}

	total := 0
	for _, v := range sorted {
		total += v[1]
		if total >= nm[1] {
			fmt.Println(v[0])
			return
		}
	}
}