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 <bits/stdc++.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

using namespace std;

typedef long long int lli;
typedef pair<int, int> ii;

template<class T>bool chmax(T &a, const T &b) { if( a < b ) { a = b; return 1; } return 0;}
template<class T>bool chmin(T &a, const T &b) { if( b < a ) { a = b; return 1; } return 0;}

#ifdef LOCAL
	#define eprintf(...) printf(__VA_ARGS__)
#else
	#define eprintf(...) 1
#endif

#define ROUNDUP(a, b) 		( ((a) + ((b) - 1) ) / b)
#define SET_ZERO(a)	 		( memset((a), 0, sizeof(a)))
#define SET_NUM_ARRAY(a,b)	( memset((a), b, sizeof(a)))
//#define int long long int //dont forget to change int to signed

int main() {
	int N;
	lli K;
	scanf("%d %lld", &N, &K);
	priority_queue<int, vector<int>, greater<int> > Q;
	int ba[100100];
	SET_ZERO(ba);
	for (int i = 0 ; i < N; i++) {
		int a, b;
		scanf("%d %d", &a, &b);
		Q.push(a);
		ba[a] = b;
	}

	int ans;
	do {
		ans = Q.top(); Q.pop();
		K -= ba[ans];
	} while (K > 0);

	printf("%d\n", ans);
	return 0;
}