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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
#include <vector>  
#include <map>
main(){
    uint32_t N, a, b;
    uint64_t K, cnt = 0;
    std::cin >> N >> K;
    std::map<uint32_t, uint32_t> mp;
    for(uint32_t i = 0; i < N; i++)
    {
        std::cin >> a >> b;
        if(mp.find(a) == mp.end())
        {
            mp[a] = b;
        }
        else 
        {
            mp[a] += b;
        }
    }
    for(std::map<uint32_t, uint32_t>::iterator itr = mp.begin(); itr != mp.end(); ++itr) 
    {
        cnt += itr->second;
        if(cnt >= K)
        {
            std::cout << itr->first << "\n"; 
            break;
        }
    }
    
}