Count Pair Combinations

You are given a sequence of N positive integers. Your task is to count the number of distinct pairs (i, j) such that 1 ≤ i < j ≤ N. Although the sequence is provided as input, the answer depends solely on the value of N.

Recall that the total number of ways to choose 2 distinct indices from N elements is given by the formula:

\( \frac{N \times (N-1)}{2} \)

Compute and output this number.

inputFormat

The input is read from stdin and consists of two lines:

• The first line contains a single integer N (the number of elements in the sequence).
• The second line contains N space-separated positive integers representing the sequence.

outputFormat

Output a single integer to stdout which is the number of valid pairs (i, j) satisfying 1 ≤ i < j ≤ N.

Note: You do not need to use the sequence values for the computation.

## sample

5
1 2 3 4 5

10

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