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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int num[100005];

typedef long long ll;

int main(){

	int N;

	ll K;

	scanf("%d %lld",&N,&K);

	int i;

	int a, b;

	for (i = 0; i < N; i++) {
		scanf("%d %d",&a,&b);
		num[a] += b;
	}

	ll ans = 0ll;
	for (i = 1; i <= 100000; i++) {
		if (num[i] > 0) {
			if (ans + 1ll<=K && K<=ans + (ll)num[i]) {
				printf("%d\n",i);
				return 0;
			}
			ans += (ll)num[i];
		}
	}

	return 0;
}