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>

int main()
{
    int N,i,j,k,a,b,K,c[100001],d[100001],small,sum=0;
    scanf("%d%d",&N,&K);
    for(i=0;i<N;i++){
        scanf("%d%d",&a,&b);
        if(i==0){
            c[0]=a;d[0]=b;k=1;
        }
        else{
            for(j=0;j<k;j++){
                if(c[j]==a){
                    d[j]+=b;
                    break;
                }
                else if(j==k-1){
                    c[k]=a;d[k]=b;k++;
                    break;
                }
            }
        }
    }
    for(i=1;i<k;i++){
        for(j=i;j>0;j--){
            if(c[j]<c[j-1]){
                small=c[j];
                c[j]=c[j-1];
                c[j-1]=small;
                small=d[j];
                d[j]=d[j-1];
                d[j-1]=small;
            }
        }
    }
    for(i=0;i<k;i++){
        sum+=d[i];
        if(sum>=K){
            printf("%d\n",c[i]);
            break;
        }
    }
    return 0;
}