subtractive_generator: procedure options (main);

   declare (r, s) (0:54) fixed binary (31);
   declare (i, n, seed)  fixed binary (31);

   /* Bentley's initialization */
   seed = 292929;
   s(0) = seed; s(1) = 1;

   /* Compute s2,s3,...,s54 using the subtractive formula sn = s(n-2) - s(n-1)(mod 10**9). */
   do n = 2 to hbound(s,1);
      s(n) = mod ( s(n-2) - s(n-1), 1000000000);
   end;

   /* Rearrange initial values. */
   do n = 0 to hbound(r,1);
      r(n) = s( mod(34*(n+1), 55));
   end;

   do n = 55 to 219;
      i = mod (n, 55);
      r(i) = mod ( r(mod(n-55, 55)) - r(mod(n-24, 55)), 1000000000);
   end;

   do n = 220 to 235;
      i = mod(n, 55);
      r(i) = mod ( r(mod(n-55, 55)) - r(mod(n-24, 55)), 1000000000);
      put skip list (r(i));
   end;

end subtractive_generator;