How to get the the program to stop?

I'm creating a program and need it to stop at a prompted number.

if true
  % code
end
*n = input('Enter number of grades in range: ');
while n<0    
  x=input('Enter grade(0 to 100): ');
  if x >= 90
      fprintf('Grade = %0.0f,A\n',x)
  elseif x >= 80
      fprintf('Grade = %0.0f,B\n',x)
  elseif x >= 70
      fprintf('Grade = %0.0f,C\n',x)
  elseif x >=60
      fprintf('Grade = %0.0f,D\n',x)
  else
      fprintf('Grade = %0.0f,F\n',x)
  end
  if x<0
  end
end*

After prompting the user to enter the number of grades, n, I need my while loop to stop after that number of entries of x.

Could I use an array for this? Or is what I have okay?