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Count number of hops
Easy Accuracy: 46.41% Submissions: 21895 Points: 2

A frog jumps either 1, 2, or 3 steps to go to the top. In how many ways can it reach the top. As the answer will be large find the answer modulo 1000000007.

Example 1:

Input:
N = 1
Output: 1


Example 2:

Input:
N = 4
Output: 7
Explanation:Below are the 7 ways to reach
4
1 step + 1 step + 1 step + 1 step
1 step + 2 step + 1 step
2 step + 1 step + 1 step
1 step + 1 step + 2 step
2 step + 2 step
3 step + 1 step
1 step + 3 step

Your task is to complete the function countWays() which takes 1 argument(N) and returns the answer%(10^9 + 7).

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 ≤ N ≤ 105