Challenge: Last Digit of the Partial Sum of Fibonacci Numbers

Problem

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Last Digit of the Partial Sum of Fibonacci Numbers

Compute the last digit of $F_{m} + F_{m+1} + \cdot\cdot\cdot + F_{n}$.

Input: Integers $m \leq n$.

Output: The last digit of $F_{m} + F_{m+1} + \cdot\cdot\cdot + F_{n}$ ...