# Java Program for nth multiple of a number in Fibonacci Series

Given two integers n and k. Find position the n’th multiple of K in the Fibonacci series.

Examples:

Input : k = 2, n = 3 Output : 9 3'rd multiple of 2 in Fibonacci Series is 34 which appears at position 9. Input : k = 4, n = 5 Output : 30 5'th multiple of 5 in Fibonacci Series is 832040 which appears at position 30.

An **Efficient Solution **is based on below interesting property.

Fibonacci series is always periodic under modular representation. Below are examples.

F (mod 2) = 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0 Here 0 is repeating at every 3rd index and the cycle repeats at every 3rd index. F (mod 3) = 1, 1, 2, 0, 2, 2, 1, 0, 1, 1, 2, 0, 2, 2, 1, 0, 1, 1, 2, 0, 2, 2, 1, 0, 1, 1, 2, 0, 2, 2 Here 0 is repeating at every 4th index and the cycle repeats at every 8th index. F (mod 4) = 1, 1, 2, 3, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 3, 1, 0 Here 0 is repeating at every 6th index and the cycle repeats at every 6th index. F (mod 5) = 1, 1, 2, 3, 0, 3, 3, 1, 4, 0, 4, 4, 3, 2, 0, 2, 2, 4, 1, 0, 1, 1, 2, 3, 0, 3, 3, 1, 4, 0 Here 0 is repeating at every 5th index and the cycle repeats at every 20th index. F (mod 6) = 1, 1, 2, 3, 5, 2, 1, 3, 4, 1, 5, 0, 5, 5, 4, 3, 1, 4, 5, 3, 2, 5, 1, 0, 1, 1, 2, 3, 5, 2 Here 0 is repeating at every 12th index and the cycle repeats at every 24th index. F (mod 7) = 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6, 1, 0, 1, 1, 2, 3, 5, 1, 6, 0, 6, 6, 5, 4, 2, 6 Here 0 is repeating at every 8th index and the cycle repeats at every 16th index. F (mod 8) = 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0, 5, 5, 2, 7, 1, 0, 1, 1, 2, 3, 5, 0 Here 0 is repeating at every 6th index and the cycle repeats at every 12th index. F (mod 9) = 1, 1, 2, 3, 5, 8, 4, 3, 7, 1, 8, 0, 8, 8, 7, 6, 4, 1, 5, 6, 2, 8, 1, 0, 1, 1, 2, 3, 5, 8 Here 0 is repeating at every 12th index and the cycle repeats at every 24th index. F (mod 10) = 1, 1, 2, 3, 5, 8, 3, 1, 4, 5, 9, 4, 3, 7, 0, 7, 7, 4, 1, 5, 6, 1, 7, 8, 5, 3, 8, 1, 9, 0. Here 0 is repeating at every 15th index and the cycle repeats at every 60th index.

`// Java Program to find position of n'th multiple` `// of a mumber k in Fibonacci Series` `package` `gfg;` `public` `class` `GFG {` ` ` `public` `static` `int` `findPosition(` `int` `k, ` `int` `n)` ` ` `{` ` ` `long` `f1 = ` `0` `, f2 = ` `1` `, f3;` ` ` `int` `i = ` `2` `;` ` ` ` ` `while` `(i != ` `0` `) {` ` ` `f3 = f1 + f2;` ` ` `f1 = f2;` ` ` `f2 = f3;` ` ` ` ` `if` `(f2 % k == ` `0` `) {` ` ` `return` `n * i;` ` ` `}` ` ` ` ` `i++;` ` ` `}` ` ` `return` `0` `;` ` ` `}` ` ` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` `// Multiple no.` ` ` `int` `n = ` `5` `;` ` ` ` ` `// Number of whose multiple we are finding` ` ` `int` `k = ` `4` `;` ` ` ` ` `System.out.print(` `"Position of n'th multiple"` `+` ` ` `" of k in Fibonacci Series is "` `);` ` ` ` ` `System.out.println(findPosition(k, n));` ` ` `}` `}` ` ` `// Code contributed by Mohit Gupta_OMG` |

**Output:**

Please refer complete article on n’th multiple of a number in Fibonacci Series for more details!