102062: [AtCoder]ABC206 C - Swappable
Memory Limit：256 MB
Time Limit：2 S
Judge Style：Text Compare
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Submit：0
Solved：0
Description
Score : $300$ points
Problem Statement
Given an array of $N$ integers $A=(A_1,A_2,...,A_N)$, find the number of pairs $(i,j)$ of integers satisfying all of the following conditions:
- $1 \le i < j \le N$
- $A_i \neq A_j$
Constraints
- All values in input are integers.
- $2 \le N \le 3 \times 10^5$
- $1 \le A_i \le 10^9$
Input
Input is given from Standard Input in the following format:
$N$ $A_1$ $A_2$ $\dots$ $A_N$
Output
Print the answer as an integer.
Sample Input 1
3 1 7 1
Sample Output 1
2
In this input, we have $A=(1,7,1)$.
- For the pair $(1,2)$, $A_1 \neq A_2$.
- For the pair $(1,3)$, $A_1 = A_3$.
- For the pair $(2,3)$, $A_2 \neq A_3$.
Sample Input 2
10 1 10 100 1000 10000 100000 1000000 10000000 100000000 1000000000
Sample Output 2
45
Sample Input 3
20 7 8 1 1 4 9 9 6 8 2 4 1 1 9 5 5 5 3 6 4
Sample Output 3
173