Lucky PIN

AtCoder

IDsumitb2019_d

Time2000ms

Memory256MB

Difficulty—

AtCoder Inc. has decided to lock the door of its office with a $3$\-digit PIN code. The company has an $N$\-digit lucky number, $S$. Takahashi, the president, will erase $N-3$ digits from $S$ and concatenate the remaining $3$ digits without changing the order to set the PIN code. How many different PIN codes can he set this way? Both the lucky number and the PIN code may begin with a $0$. ## Constraints * $4 \leq N \leq 30000$ * $S$ is a string of length $N$ consisting of digits. ## Input Input is given from Standard Input in the following format: $N$ $S$ [samples]

Samples

Input #1

4
0224

Output #1

3

Takahashi has the following options:

*   Erase the first digit of $S$ and set `224`.
*   Erase the second digit of $S$ and set `024`.
*   Erase the third digit of $S$ and set `024`.
*   Erase the fourth digit of $S$ and set `022`.

Thus, he can set three different PIN codes: `022`, `024`, and `224`.

Input #2

6
123123

Output #2

Input #3

19
3141592653589793238

Output #3

API Response (JSON)

{
  "problem": {
    "name": "Lucky PIN",
    "description": {
      "content": "AtCoder Inc. has decided to lock the door of its office with a $3$\\-digit PIN code. The company has an $N$\\-digit lucky number, $S$. Takahashi, the president, will erase $N-3$ digits from $S$ and conc",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "sumitb2019_d"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "AtCoder Inc. has decided to lock the door of its office with a $3$\\-digit PIN code.\nThe company has an $N$\\-digit lucky number, $S$. Takahashi, the president, will erase $N-3$ digits from $S$ and conc...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments