Socks

AtCoder

IDabc295_c

Time4000ms

Memory256MB

Difficulty—

You have $N$ socks. The color of the $i$\-th sock is $A_i$. You want to perform the following operation as many times as possible. How many times can it be performed at most? * Choose two same-colored socks that are not paired yet, and pair them. ## Constraints * $1\leq N \leq 5\times 10^5$ * $1\leq A_i \leq 10^9$ * All values in the input are integers. ## Input The input is given from Standard Input in the following format: $N$ $A_1$ $A_2$ $\dots$ $A_N$ [samples]

Samples

Input #1

6
4 1 7 4 1 4

Output #1

2

You can do the operation twice as follows.

*   Choose two socks with the color $1$ and pair them.
*   Choose two socks with the color $4$ and pair them.

Then, you will be left with one sock with the color $4$ and another with the color $7$, so you can no longer do the operation. There is no way to do the operation three or more times, so you should print $2$.

Input #2

1
158260522

Output #2

Input #3

10
295 2 29 295 29 2 29 295 2 29

Output #3

API Response (JSON)

{
  "problem": {
    "name": "Socks",
    "description": {
      "content": "You have $N$ socks. The color of the $i$\\-th sock is $A_i$. You want to perform the following operation as many times as possible. How many times can it be performed at most? *   Choose two same-colo",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 4000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc295_c"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You have $N$ socks. The color of the $i$\\-th sock is $A_i$.\nYou want to perform the following operation as many times as possible. How many times can it be performed at most?\n\n*   Choose two same-colo...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments