changumangu23
Changu and Mangu are brothers. Changu likes 2 and Mangu likes 3. They decided to express each number as sum of 2 and 3.
They need your help. They want you to tell them the number of ways of writing a number n as an ordered sum of 2s and/or 3s.
Example
For n = 8, the output should be changumangu23(n) = 4.
There are 4 ways to write 8 as an unordered sum of 2s and/or 3s:
2 + 2 + 2 + 2;2 + 3 + 3;3 + 2 + 3;3 + 3 + 2.
Input/Output
-
[execution time limit] 1 seconds
-
[input] integer n
The given number
n.Constraints:
0 ≤ n < 106. -
[output] integer
- The number of ways to write
nas an ordered sum of2s and/or3s modulo109 + 7.
- The number of ways to write
Post Comment