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<string.h>
#include<math.h>
#include<stdlib.h>
#include<limits.h>

#define rep(i,begin,end) for(int i=begin; i<end; i++)
#define lld long long int

typedef struct node{
    lld a, b;
}node;

int cmpAsc(const void* a, const void* b){
    lld x = ((node*)a)->a, y = ((node*)b)->a;
    if(x > y){
        return 1;
    }
    if(x < y){
        return -1;
    }
    return 0;
}

int main(){
    int n;
    lld k;
    scanf("%d %lld", &n, &k);
    node a[n];
    rep(i, 0, n){
        scanf("%lld %lld", &a[i].a, &a[i].b);
    }
    qsort(a, n, sizeof(node), cmpAsc);
    int x = 0;
    while(k > 0){
        k -= a[x].b;
        if(k>0){
            x++;
        }
    }
    printf("%lld", a[x].a);

    return 0;
}