Given an integer sequence, you are asked to compute how many pairs are there in the sequence.
Pair definition: if sequence[a] = sequence[b] and a < b, then sequence[a] and sequence[b] are pairs. (a , b are index)
For example:
Input sequence = 1 2 4 1 9 7 2 3 1 8
There are 4 pairs which index pairs are (0, 3), (0, 8), (1, 6), (3, 8) in this sequence .
First line contains an integer N which denotes the length of the input sequence. (1 ≤ N ≤ 100000)
Second line contains N integer which denote the input sequence. (0 ≤ each number in input sequence ≤ 10000)
An integer which denote the number of pairs in the sequence.
Remember to print a newline('\n') at the end of the last line.