Pair with Sum

Given an array of n integers and an integer target k, determine whether there exist two distinct elements in the array whose sum is exactly k. If such a pair exists, output YES; otherwise, output NO.

The problem can be formulated mathematically as follows: Find indices \(i\) and \(j\) with \(i \neq j\) such that \[ a_i + a_j = k, \] where \(a_1, a_2, \ldots, a_n\) are the elements of the array.

Note: The input is taken from the standard input and the result is printed to the standard output.

inputFormat

The first line contains two integers n and k separated by a space, where n denotes the number of elements in the array and k is the target sum.

The second line contains n integers separated by spaces representing the elements of the array.

outputFormat

Output a single line containing either YES if there exists a pair of distinct indices such that their corresponding array elements sum to k, or NO if no such pair exists.

5 9
2 7 11 15 1

YES