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: Wrong Answer)

#include <stdio.h>
void swap(int x, int y){
    int temp;
    temp=x;
    x=y;
    y=temp;
}
int main(void){
    long N,K,i,j,g=0;
    scanf("%ld%ld",&N,&K);
    long a[N],b[N];
    scanf("%ld %ld",&a[0],&b[0]);
    for(i=1;i<N;i++){
        scanf("%ld%ld",&a[i],&b[i]);
        j=i;
        while((j<0)&&(a[j-1]>a[j])){
            swap(a[j-1],a[j]);
            swap(b[j-1],b[j]);
            j--;
        }
    }
    for(i=0;g<N;i++){
        g+=b[i];
    }
    printf("%ld\n",a[i]);
}