Find Unique Pairs with Given Sum

You are given an array of integers and a target integer \(T\). Your task is to find and report all unique pairs \((a, b)\) such that \(a + b = T\). Each pair must satisfy \(a \le b\) (i.e. the pair is in ascending order) and duplicate pairs should be discarded.

Input Format: The first line contains an integer \(N\) which denotes the number of elements in the array. The second line contains \(N\) space-separated integers representing the array elements. The third line contains an integer representing the target sum \(T\).

Output Format: If one or more valid pairs exist, print each unique pair on a new line where the two numbers are separated by a space, and the pairs are sorted in ascending order based on their first then second elements. If no such pair exists, print None.

inputFormat

The input is read from standard input (stdin) and consists of three lines:

• Line 1: An integer \(N\) indicating the number of elements in the array.
• Line 2: \(N\) space-separated integers representing the array.
• Line 3: An integer \(T\), the target sum.

outputFormat

The output should be printed to standard output (stdout). For each pair found, output a line containing the two integers separated by a space. Pairs must be unique and each pair's two numbers must be in ascending order. If no valid pair exists, output a single line with the text None.

## sample

6
1 2 3 4 5 6
7

1 6
2 5
3 4

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