It is November 18 now in Japan. By the way, 11 and 18 are adjacent Lucas numbers.
You are given an integer N. Find the N-th Lucas number.
Here, the i-th Lucas number L_i is defined as follows:
- L_0=2
- L_1=1
- L_i=L_{i-1}+L_{i-2} (i≥2)

-----Constraints-----
- 1≤N≤86
- It is guaranteed that the answer is less than 10^{18}.
- N is an integer.

-----Input-----
Input is given from Standard Input in the following format:
N

-----Output-----
Print the N-th Lucas number.

-----Sample Input-----
5

-----Sample Output-----
11

• L_0=2
• L_1=1
• L_2=L_0+L_1=3
• L_3=L_1+L_2=4
• L_4=L_2+L_3=7
• L_5=L_3+L_4=11
  Thus, the 5-th Lucas number is 11.

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