Problems > Rabbit Pairs

Rabbit Pairs

Difficulty: 1700 4000 ms 128 MB

math matrix-exponentiation

A pair of rabbits produces a new pair every month starting from their second month; no rabbit dies. Starting from one newborn pair in month 1, count the pairs in month N, modulo 109+7.

Input: one integer N.

Output: the value modulo 109+7.

Constraints:

  • 1 ≤ N ≤ 1018

Sample Tests

Input 1
5
Output 1
5
Input 2
1
Output 2
1

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