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Number of ways in which N can be represented as the sum of two positive integers
• Last Updated : 26 Mar, 2021

Given a number N, the task is to find the number of unique ways in which N can be represented as a sum of two positive integers.
Examples:

Input: N = 7
Output:
(1 + 6), (2 + 5) and (3 + 4).
Input: N = 200
Output: 100

Approach: The number of ways in which the number can be expressed as the sum of two positive integers are 1 + (N – 1), 2 + (N – 2), …, (N – 1) + 1 and (N – 2) + 2. There are N – 1 terms in the series and they appear in identical pairs i.e. (X + Y, Y + X). So the required count will be N / 2.
Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;` `// Function to return the number of``// distinct ways to represent n``// as the sum of two integers``int` `ways(``int` `n)``{``    ``return` `n / 2;``}` `// Driver code``int` `main()``{``    ``int` `n = 2;` `    ``cout << ways(n);` `    ``return` `0;``}`

## Java

 `// Java implementation of the approach` `class` `GFG``{``    ` `    ``// Function to return the number of``    ``// distinct ways to represent n``    ``// as the sum of two integers``    ``static` `int` `ways(``int` `n)``    ``{``        ``return` `n / ``2``;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `n = ``2``;``    ` `        ``System.out.println(ways(n));``    ``}``}` `// This code is contributed by AnkitRai01`

## Python3

 `# Python3 implementation of the approach` `# Function to return the number of``# distinct ways to represent n``# as the sum of two integers``def` `ways(n):``    ``return` `n ``/``/` `2` `# Driver code``n ``=` `2` `print``(ways(n))` `# This code is contributed by Mohit Kumar`

## C#

 `// C# implementation of the approach``using` `System;` `class` `GFG``{``    ` `// Function to return the number of``// distinct ways to represent n``// as the sum of two integers``static` `int` `ways(``int` `n)``{``    ``return` `n / 2;``}` `// Driver code``public` `static` `void` `Main()``{``    ``int` `n = 2;` `    ``Console.WriteLine(ways(n));``}``}` `// This code is contributed by Nidhi_Biet`

## Javascript

 ``
Output:
`1`

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