Given a number N, evaluate the following expression.
f(n-1)f(n+1) - f(n)f(n) where f(n) is the n-th Fibonacci number with n >= 1.
Fibonacci Sequence is 0, 1, 1, 2, 3, 5, 8, 13,… (here 0 is the 0th Fibonacci number)
Example 1:
Input: N = 1
Output: 1
Explaination: f(n+1)f(n-1) - f(n)f(n)
= 10 - 11 = -1.
Example 2:
Input: N = 2
Output: 1
Explaination: f(n+1)f(n-1) - f(n)f(n)
= 21 - 11 = 1.
Your Task:
You do not need to read input or print anything. Your Task is to complete the function fibExpresssion() which takes the value N as input parameters and returns the required difference.
Expected Time Complexity: O(1)
Expected Auxiliary Space: O(1)
Constraints:
1 ≤ N ≤ 10^{5}

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