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: Accepted)

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

typedef struct {
  int number;
  int kazu;
} set;

int cmp( const void *p, const void *q ) {
    return ((set*)p)->number - ((set*)q)->number;
}

int main(){
  int i,j,k,N;
  long K;
  
  scanf("%d %ld",&N,&K);
  set A[N];
  for(i=0;i<N;i++){
    scanf("%d %d",&A[i].number,&A[i].kazu);
  }
  qsort(A,sizeof(A) / sizeof(set),sizeof(set),cmp);
  i=0;
  while(K>0){
    K-=A[i].kazu;
    i++;
  }
  printf("%d\n",A[i-1].number);
  return 0;
}