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 9.2.1) (judge verdict: Runtime Error)

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

#define ll long long


typedef struct list{
    int a, b;
    struct list *p;
}li;

int main(void){
    int n, a, b;
    ll k;
    li *pnow, *_p;//検索用と計算用のポインタ
    li *ps = malloc(sizeof(li));//先頭ポインタ

    ps -> p = NULL;
    ps -> a = 0;
    ps -> b = 0;
    scanf("%d %lld", &n, &k);

    for(int i = 0; i < n; i++){
        scanf("%d %d", &a, &b);
        pnow = ps;
        while(1){
            if(a > pnow -> a){
                if(pnow -> p == NULL || pnow -> p -> a > a){
                    _p = pnow -> p;
                    pnow -> p = malloc(sizeof(li));
                    pnow = pnow -> p;

                    pnow -> p = _p;
                    pnow -> a = a;
                    pnow -> b = b;
                    break;
                }else{
                    pnow = pnow -> p;
                }
            }else if(a == pnow -> a){
                pnow -> b += b;
                break;
            }
        }
    }
    pnow = ps;
    while(k > 0){
        pnow = pnow -> p;
        k -= pnow -> b;
    }
    printf("%d", pnow -> a);

    return 0;
}