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: Runtime Error)

#include <stdio.h>
#include <stdlib.h>

int main(void) {
	int K;
	int *A;
	int ai[100000], bi[100000];
	int n;
	int i, j, k = 0;
	int min;
	int tmp;
	
	scanf("%d %d", &n, &K);
	
	for (i = 0; i < n; i++) {
		scanf("%d %d", &ai[i], &bi[i]);
	}
	
	A = (int *)malloc(n * bi[n-1] * sizeof(int));

	for (i = 0; i < bi[i]; i++) {
		for (j = 0; j < bi[j]; j++) {
			A[k] = ai[i];
			k++;
		}
	}
	
	for (i = 0; i < n; i++) {
		for (j = i; j < n; j++) {
			if (A[i] > A[j]) {
				min = A[j];
			}
		}
		tmp = A[i];
		A[i] = A[j];
		A[j] = tmp;
	}
	

	
	printf("%d\n", A[k - 1]);

	return 0;
}