TODO: Find the last digit of a partial sum of
Fibonacci Numbers: Given two non-negative integers m and n,
where m <= n, find the last digit of the sum Fm + Fm+1 … + Fn
TODO: Find the last digit of a partial sum of
Fibonacci Numbers: Given two non-negative integers m and n,
where m <= n, find the last digit of the sum Fm + Fm+1 … + Fn