theorem Th39:
  m * n = 626 implies m = 1 & n = 626
                   or m = 2 & n = 313
                   or m = 313 & n = 2
                   or m = 626 & n = 1
  proof
    assume
A1: m*n = 626;
    m divides m*n;
    then m = 1 or m = 2 or m = 313 or m = 626 by A1,Th25;
    hence thesis by A1;
  end;
