theorem Th13:
  InsCode I = 2 implies ex a, b st I = AddTo(a,b)
proof
A1: I = [0,{},{}] or (ex a,b st I = a:=b) or (ex a,b st I = AddTo(a,b)) or (ex
  a,b st I = SubFrom(a,b)) or (ex a,b st I = MultBy(a,b)) or
   (ex i1 st I = goto(i1,R)) or
    (ex a,i1 st I = a=0_goto i1) or ex a,r st I = a:=r by SCMRING2:7;
  assume InsCode I = 2;
  hence thesis by A1;
end;
