begin
owninteger nextsym=4
integer opd
opd=23
unless 20<=opd<=nextsym+20 then printstring(" bug1 
")
if 20<=opd<=nextsym+20 then opd=opd else printstring(" bug2 
")
unless opd>=20  and opd<=nextsym+20 then printstring(" bug3 
")

endofprogram