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<bits/stdc++.h>
#define REP(i, n) for (int i=0; i<n; ++i)
#define print(x) cout << x << endl;
typedef long long ll;

using namespace std;

void solve() {
    const int M = 100001;
    ll N, K;
    cin >> N >> K;
    ll d[M];
    REP(i, M) d[i] = 0;
    REP(i, N) {
        ll a, b;
        cin >> a >> b;
        d[a] += b;
    }
    ll cnt = 0;
    ll ans;
    REP(i, M) {
        cnt += d[i];
        if (cnt >= K) {
            ans = i;
            break;
        }
    }
    print(ans);
}

int main() {

    solve();
    return 0;
}