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: Accepted)

#include <bits/stdc++.h>
using namespace std;

const int DIM = 1e5 + 5;

long long cnt[DIM];

int main( void ) {
    
    int n; long long k;
    cin >> n >> k;
    
    for( int i = 1; i <= n; i ++ ) {
        int x, y;
        cin >> x >> y;
        
        cnt[x] += y;
    }
    
    for( int i = 1; i <= 1e5; i ++ ) {
        if( k <= cnt[i] ) {
            cout << i << endl;
            break;
        }
        else
            k -= cnt[i];
    }
    
    return 0;
}