MATLAB: Using while loops, to sort and index arrays.

arrayMATLABwhile loops

Can some one please help me with a homework problem thats driving me crazy!!
I need to make a function that scans the grades of a class, each time it sees a fail, a counter goes up by one.
This counter then saves the grade and position of the failing grade on the list.
This has to be done using a 'While loop"
I have written working code, however, my while loop is just as frivolous as the counter in countroles. 
Marks = randi([0 100],1,10)
Fail = [0:40]; 
no = ismember([Marks],[Fail]);
B = sum(no);
Counter = 0;
while Counter < B
    Counter = Counter + 1
end
[c,x] = find(no == 1);
Index = x
Results = Marks(x)
if a == 0
    Results = "'Happy Days, No Fails' "
    Index = 0
end
Thank you!

Best Answer

Maybe you can use anything like:
Marks = randi([0 100],1,10)
Fail = [0:40]; 
i=1;
FailCount=0;
while i<=length(Marks)
    if any(Marks(i)<=(Fail))
        FailCount=FailCount+1;
    end                     
    i=i+1;
end
But to be honest I'm curious about the homework since this is a really bad problem or bad idea to use a while loop since 
sum(ismember(Marks,Fail))
solves the problem and 
find(ismember(Marks,Fail)==1)
gives the positions of Fails.
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