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 C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("3 4");
            WillReturn.Add("1 1");
            WillReturn.Add("2 2");
            WillReturn.Add("3 3");
            //3
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("10 500000");
            WillReturn.Add("1 100000");
            WillReturn.Add("1 100000");
            WillReturn.Add("1 100000");
            WillReturn.Add("1 100000");
            WillReturn.Add("1 100000");
            WillReturn.Add("100000 100000");
            WillReturn.Add("100000 100000");
            WillReturn.Add("100000 100000");
            WillReturn.Add("100000 100000");
            WillReturn.Add("100000 100000");
            //1
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(X => int.Parse(X)).ToArray();

        SplitAct(InputList[0]);
        int K = wkArr[1];

        var CntDict = new Dictionary<int, int>();
        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);

            int wkKey = wkArr[0];
            int wkValue = wkArr[1];

            if (CntDict.ContainsKey(wkKey) == false) {
                CntDict.Add(wkKey, wkValue);
            }
            else CntDict[wkKey] += wkValue;
        }

        int RestCnt = K;
        foreach (var EachPair in CntDict.OrderBy(X=>X.Key)) {
            RestCnt -= EachPair.Value;
            if (RestCnt <= 0) {
                Console.WriteLine(EachPair.Key);
                break;
            }
        }
    }
}