100HOME:INPUT"ENTER A STRING:";S$:FORL=1TOLEN(S$):I$=MID$(S$,L,1):LC=(ASC(I$)>95)*32:C$=CHR$(ASC(I$)-LC):IFC$>="A"ANDC$<="Z"THENC$=CHR$(ASC(C$)+13):C$=CHR$(ASC(C$)-26*(C$>"Z")):I$=CHR$(ASC(C$)+LC)
110A$=A$+I$:NEXT:PRINTA$