Have a Question!!

I'm currently college student in University of Texas. Im trying to write a program to check my grades.
I need to write a program to compute the grade earned by a (one) student.
The program will initially request 5 assignment scores, 2 test scores, and 1 final examination score. All scores are out of 100. If any input score is out of range (negative or above 100), output an error statement and terminate the program. Also I need to use bool (in C++) to record whether a score is out-of-range or not.
Calculate the score of the student based on the following weights:
85<= score <= 100 A
74 <= score < 85 B
63 <= score < 74 C
52 <= score < 63 D
0 <= score < 52 F

P.s
I do not want to use "if" or "else" for this program.
please help me on this. I have no idea how to start with it.

No idea where to start?
Surely you can start with

Code:

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int main()
{
    return 0;
}

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Did you heard about case as alternatives for if ?