String►Equ("0",Y₁)
Disp "Enter S to Stop"
While 1
  Input "Y=",Str1
  If Str1="S"
    Stop
  Input "If ",Str2
  If Str2="S"
    Stop
  Equ►String(Y₁,Str3)
  String►Equ(Str3+"+("+Str1+")("+Str2+")",Y₁)
End