Given a range i.e. L and R, the task is to find if we can form pairs such that GCD of every pair is 1. Every number in the range L-R should be involved exactly in one pair.**Examples:**

Input: L = 1, R = 8 Output: Yes {2, 7}, {4, 1}, {3, 8}, {6, 5} All pairs have GCD as 1. Input: L = 2, R = 4 Output: No

**Approach**: Since every number in the range(L, R) must be included exactly once in every pair. Hence if L-R is an even number, then it is not possible. If L-R is an odd number, then print all the adjacent pairs since adjacent pairs will always have GCD as 1.

Below is the implementation of the above approach:

## C++

`// C++ program to print all pairs` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to print all pairs` `bool` `checkPairs(` `int` `l, ` `int` `r)` `{` ` ` `// check if even` ` ` `if` `((l - r) % 2 == 0)` ` ` `return` `false` `;` ` ` `/* We can print all adjacent pairs` ` ` `for (int i = l; i < r; i += 2) {` ` ` `cout << "{" << i << ", " << i + 1 << "}, ";` ` ` `} */` ` ` ` ` `return` `true` `;` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `l = 1, r = 8;` ` ` `if` `(checkPairs(l, r))` ` ` `cout << ` `"Yes"` `;` ` ` `else` ` ` `cout << ` `"No"` `;` ` ` `return` `0;` `}` |

## Java

`// Java program to print all pairs` `class` `GFG` `{` `// Function to print all pairs` `static` `boolean` `checkPairs(` `int` `l, ` `int` `r)` `{` ` ` `// check if even` ` ` `if` `((l - r) % ` `2` `== ` `0` `)` ` ` `return` `false` `;` ` ` `/* We can print all adjacent pairs` ` ` `for (int i = l; i < r; i += 2)` ` ` `{` ` ` `System.out.print("{"+i+", "+i + 1+"}, ");` ` ` `} */` ` ` ` ` `return` `true` `;` `}` `// Driver Code` `public` `static` `void` `main(String[] args)` `{` ` ` `int` `l = ` `1` `, r = ` `8` `;` ` ` `if` `(checkPairs(l, r))` ` ` `System.out.println(` `"Yes"` `);` ` ` `else` ` ` `System.out.println(` `"No"` `);` `}` `}` `// This code is contributed by mits` |

## Python 3

`# Python 3 program to print all pairs` `# Function to print all pairs` `def` `checkPairs(l, r) :` ` ` `# check if even` ` ` `if` `(l ` `-` `r) ` `%` `2` `=` `=` `0` `:` ` ` `return` `False` ` ` `""" we can print all adjacent pairs` ` ` `for i in range(l,r,2) :` ` ` `print("{",i,",",i + 1, "},")` ` ` `"""` ` ` ` ` `return` `True` `# Driver Code` `if` `__name__ ` `=` `=` `"__main__"` `:` ` ` `l, r ` `=` `1` `, ` `8` ` ` `if` `checkPairs(l, r) :` ` ` `print` `(` `"Yes"` `)` ` ` `else` `:` ` ` `print` `(` `"No"` `)` ` ` `# This code is contributed by ANKITRAI1` |

## C#

`// C# program to print all pairs` `using` `System;` `class` `GFG` `{` `// Function to print all pairs` `static` `bool` `checkPairs(` `int` `l, ` `int` `r)` `{` ` ` `// check if even` ` ` `if` `((l - r) % 2 == 0)` ` ` `return` `false` `;` ` ` `/* We can print all adjacent pairs` ` ` `for (int i = l; i < r; i += 2)` ` ` `{` ` ` `System.out.print("{"+i+", "+i + 1+"}, ");` ` ` `} */` ` ` ` ` `return` `true` `;` `}` `// Driver Code` `static` `public` `void` `Main ()` `{` ` ` `int` `l = 1, r = 8;` ` ` `if` `(checkPairs(l, r))` ` ` `Console.Write(` `"Yes"` `);` ` ` `else` ` ` `Console.Write(` `"No"` `);` `}` `}` `// This code is contributed by Raj` |

## PHP

`<?php` `// PHP program to print all pairs` `// Function to print all pairs` `function` `checkPairs(` `$l` `, ` `$r` `)` `{` ` ` `// check if even` ` ` `if` `((` `$l` `- ` `$r` `) % 2 == 0)` ` ` `return` `false;` ` ` `/* We can print all adjacent pairs` ` ` `for (int i = l; i < r; i += 2)` ` ` `{` ` ` `cout << "{" << i << ", " << i + 1 << "}, ";` ` ` `} */` ` ` ` ` `return` `true;` `}` `// Driver Code` `$l` `= 1;` `$r` `= 8;` `if` `(checkPairs(` `$l` `, ` `$r` `))` ` ` `echo` `(` `"Yes"` `);` `else` ` ` `echo` `(` `"No"` `);` ` ` `// This code is contributed` `// by Shivi_Aggarwal` `?>` |

## Javascript

`<script>` `// JavaScript program to print all pairs` ` ` `// Function to print all pairs` ` ` `function` `checkPairs(l , r) {` ` ` `// check if even` ` ` `if` `((l - r) % 2 == 0)` ` ` `return` `false` `;` ` ` `/*` ` ` `We can print all adjacent pairs` ` ` `for (i = l; i < r; i += 2) {` ` ` `document.write("{"+i+", "+i + 1+"], "); }` ` ` `*/` ` ` `return` `true` `;` ` ` `}` ` ` `// Driver Code` ` ` ` ` `var` `l = 1, r = 8;` ` ` `if` `(checkPairs(l, r))` ` ` `document.write(` `"Yes"` `);` ` ` `else` ` ` `document.write(` `"No"` `);` `// This code is contributed by todaysgaurav` `</script>` |

**Output:**

Yes

**Time Complexity:** O(N) **Auxiliary Space:** O(1)

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