A prime number is a positive whole number divisible by only itself and 1, not including 1. For example, the prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17 and 19. 

RAM[0] contains a positive whole number n <= 1000. Your goal is to output a sorted list of all the prime numbers from 1 to n into memory, starting from RAM[50] and ending the output with a -1. For example, if RAM[0] = 19, then the desired output is:

RAM[50] = 2
RAM[51] = 3
RAM[52] = 5
RAM[53] = 7
RAM[54] = 11
RAM[55] = 13
RAM[56] = 17
RAM[57] = 19
RAM[58] = -1

A good algorithm for this is the sieve of Eratosthenes:

P = Prime
X = Not prime (i.e. 0, 1, or composite)

      /-We are here
      v
0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X

      /-We are here
      v
0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X  P     X     X     X     X     X     X     X     X     X

         /-We are here
         v
0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X  P  P  X     X     X  X  X     X     X  X  X     X     X  X

            /-We are here
            v
0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X  P  P  X     X     X  X  X     X     X  X  X     X     X  X

Nothing to do here, since 4 is composite - anything divisible by 4 was divisible by 2.

               /-We are here
               v
0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X  P  P  X  P  X     X  X  X     X     X  X  X     X     X  X

And so on, until we reach n.

0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 ...
X  X  P  P  X  P  X  P  X  X  X  P  X  P  X  X  X  P  X  P  X  X

Then just scan this through and convert it to the list:

2
3
5
7
11
13
17
19
...