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>

int main(void){
  int n;
  long long k;
  scanf("%d %lld",&n,&k);
  
  long long a[100001] = {0};
  int b1 , b2;
  
  for(int i = 0;i < n;i ++){
    scanf("%d",&b1);
    scanf("%d",&b2);
    a[b1] += b2;
  }
  
  
  long long ans = 0 , c;
  for(int i = 1;i <= 100000;i ++){
    ans += a[i];
    if(ans >= k){
      c = i;
      i = 10000000;
    }
  }
  printf("%lld\n",c);
  
  return 0;
}