Distinct Trio

AtCoder

IDabc252_d

Time2000ms

Memory256MB

Difficulty—

You are given a sequence of length $N$: $A=(A_1,A_2,\ldots,A_N)$. Find the number of triples $(i,j,k)$ that satisfy both of the following conditions. * $1\leq i \lt j \lt k \leq N$ * $A_i$, $A_j$, and $A_k$ are distinct. ## Constraints * $3 \leq N \leq 2\times 10^5$ * $1 \leq A_i \leq 2\times 10^5$ * All values in input are integers. ## Input Input is given from Standard Input in the following format: $N$ $A_1$ $A_2$ $\ldots$ $A_N$ [samples]

Samples

Input #1

4
3 1 4 1

Output #1

2

The two triples $(i,j,k)$ satisfying the conditions are $(1,2,3)$ and $(1,3,4)$.

Input #2

10
99999 99998 99997 99996 99995 99994 99993 99992 99991 99990

Output #2

Input #3

15
3 1 4 1 5 9 2 6 5 3 5 8 9 7 9

Output #3

API Response (JSON)

{
  "problem": {
    "name": "Distinct Trio",
    "description": {
      "content": "You are given a sequence of length $N$: $A=(A_1,A_2,\\ldots,A_N)$.   Find the number of triples $(i,j,k)$ that satisfy both of the following conditions. *   $1\\leq i \\lt j \\lt k \\leq N$ *   $A_i$, $A_",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc252_d"
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  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You are given a sequence of length $N$: $A=(A_1,A_2,\\ldots,A_N)$.  \nFind the number of triples $(i,j,k)$ that satisfy both of the following conditions.\n\n*   $1\\leq i \\lt j \\lt k \\leq N$\n*   $A_i$, $A_...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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