Sales BY Match

There is a large pile of socks that must be paired by color. Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

Example

There is one pair of color  and one of color . There are three odd socks left, one of each color. The number of pairs is .

Function Description

Complete the sockMerchant function in the editor below.

sockMerchant has the following parameter(s):

• int n: the number of socks in the pile
• int ar[n]: the colors of each sock

Returns

• int: the number of pairs

Input Format

The first line contains an integer , the number of socks represented in .
The second line contains  space-separated integers, , the colors of the socks in the pile.

Constraints

•  where 

Sample Input

STDIN                       Function
-----                       --------
9                           n = 9
10 20 20 10 10 30 50 10 20  ar = [10, 20, 20, 10, 10, 30, 50, 10, 20]

Sample Output

3

Explanation

There are three pairs of socks.

=====================================================================

 'use strict';

const fs = require('fs');

process.stdin.resume();

process.stdin.setEncoding('utf-8');

let inputString = '';

let currentLine = 0;

process.stdin.on('data', function(inputStdin) {

    inputString += inputStdin;

});

process.stdin.on('end', function() {

    inputString = inputString.split('\n');

    main();

});

function readLine() {

    return inputString[currentLine++];

}

/*

 * Complete the 'sockMerchant' function below.

 *

 * The function is expected to return an INTEGER.

 * The function accepts following parameters:

 *  1. INTEGER n

 *  2. INTEGER_ARRAY ar

 */

function sockMerchant(n, ar) {

    // Write your code here

}

function main() {

    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    const n = parseInt(readLine().trim(), 10);

    const ar = readLine().replace(/\s+$/g, '').split(' ').map(arTemp => parseInt(arTemp, 10));

    const result = sockMerchant(n, ar);

    ws.write(result + '\n');

    ws.end();

}