Sum of the First K Fibonacci Numbers

Difficulty: 1100 2000 ms 128 MB

math

Using the sequence 1, 2, 3, 5, 8, ... print the sum of its first K terms.

Input: one integer K.

Output: the sum (it equals F(K+2) − 2 in this indexing).

Constraints:

• 1 ≤ K ≤ 85

Sample Tests

4

11

1

1

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