pair sum

/*
You have been given an integer array A and a number K. Now, you need to find out whether any two different elements of the array A sum to the 
number K. Two elements are considered to be different if they lie at different positions in the array. If there exists such a pair of numbers, 
print "YES" (without quotes), else print "NO" without quotes.

Input Format:

The first line consists of two integers N, denoting the size of array A and K. The next line consists of N space separated integers denoting 
the elements of the array A.

Output Format:

Print the required answer on a single line.

Constraints:

1≤N≤106

1≤K≤2∗106

1≤A[i]≤106

SAMPLE INPUT 
5 9
1 2 3 4 5
SAMPLE OUTPUT 
YES
Explanation
Here, A[4]+A[5]=4+5=9. So, the answer is YES.
*/

#include <bits/stdc++.h>
#define ll long long int
using namespace std;


int main()
{
   ll n, target, sum=0,flag=0;  cin>>n>>target;
   ll a[n];
   for(int i=0;i<n;i++) cin>>a[i];
   sort(a,a+n); ll l=0,h=n-1;
   while(l<h)
   {
       sum=a[l]+a[h];
       if(sum==target) { flag=1; break; }
       else if(sum>target) h--;
       else l++;
   }
  
    if(flag==1) cout<<"YES";
    else cout<<"NO";
   
}