On a wall, there are C circles. You need to connect various circles using straight lines so that the resulting figure is a planar graph with exactly F faces. Print the units digit of number of edges we can draw between various circles so as the resulting graph is planar with F faces.
Note: C and F can be very large. So, C and F are taken as String Input.

Example 1:
Input:
C = "6" , F = "10"
Output:
4
Explanation:
14 edges will be needed. Unit digit
of 14 is 4. So,Output is 4.
Example 2:
Input:
C = "100" , F = "667"
Output:
5
Explanation:
765 edges will be needed. Unit digit
of 765 is 5. So,Output is 5.

Your Task:
You don't need to read input or print anything. Your task is to complete the function findNoOfEdges() which takes Strings C and F as input and returns the answer.

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

Constraints:
1 <= C,F <= 10^{10000}

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