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++14 (GCC 5.4.1) (judge verdict: Accepted)

    #include <iostream>
	const int AMAX=100000;
    long long Z[AMAX+1];
    int main(void){
        int N;
        long long K;
        std::cin>>N>>K;
        
        for(int i=0;i<N;++i){
            int A,B;
            std::cin>>A>>B;
            Z[A]+=B;
        }
        for(int ans=1;ans<=AMAX;++ans){
            if(K<=Z[ans]){
                std::cout<<ans<<std::endl;
                break;
            }
            K-=Z[ans];
        }
    }