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: Wrong Answer)

//If you are reading this then you are at wrong place.
#include<bits/stdc++.h>
#define mod 1000000007
#define lli long long int
using namespace std;
bool prime [1000001];
void debug(lli a){cout<<a<<endl;}
lli sieve(lli a){memset(prime,true,sizeof(prime));lli p,i;for(p=2;p*p<=a;p++){if(prime[p]==true){for(i=p*2;i<=a;i+=p)prime[i]=false;}}return 0;}
lli powermod(lli _a,lli _b,lli _m){lli _r=1;while(_b){if(_b%2==1)_r=(_r*_a)%_m;_b/=2;_a=(_a*_a)%_m;}return _r;}
int main()
{
	//ifstream cin("testcase.txt");
	//ofstream cout("output.txt");	
	ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);	
	cout.precision(20);
	lli t,i,j;
	//cin>>t;
	//memset(dp, -1, sizeof dp);
	t=1;
	lli counter1=0;
	while(t--)
	{
		counter1++;
		int n,k;
		cin>>n>>k;
		vector<pair<int,int> > answer;
		int x,y;
		while(n--)
		{
			cin>>x>>y;
			answer.push_back(make_pair(x,y));
		}
		sort(answer.begin(),answer.end());
		int flag=0;
		i=0;
		while(1)
		{
			k-=answer.at(i).second;
			if(k<=0)
			{
				cout<<answer.at(i).first<<endl;
				break;
			}
			i++;
			if(i==answer.size())
			{
				flag=1;
				break;
			}
		}
		if(flag==1)
		{
			cout<<answer.at(i-1).first<<endl;
		}
		
		//cout<<"Case #"<<counter1<<" ";
		//cout<<endl;	
	}	
}