100 CLS
110 S$ = "AB" : GOSUB 160
120 S$ = "AB,CD" : GOSUB 160
130 S$ = "AB,CD,DB" : GOSUB 160
140 S$ = "HIK,AB,CD,DB,FGH" : GOSUB 160
150 END
160 DIM R$(20)
170 N = 0
180 FOR I = 1 TO LEN(S$)
190 IF MID$(S$,I,1) = "," THEN N = N+1 : GOTO 210
200 R$(N) = R$(N)+MID$(S$,I,1)
210 NEXT I
220 FOR I = 0 TO N
230 P = I
240 TS$ = ""
250 FOR J = I TO 0 STEP -1
260 IF TS$ = "" THEN P = J
270 TS$ = ""
280 FOR K = 1 TO LEN(R$(P))
290 IF J > 0 THEN IF INSTR(R$(J-1),MID$(R$(P),K,1)) = 0 THEN TS$ = TS$+MID$(R$(P),K,1)
300 NEXT K
310 IF LEN(TS$) < LEN(R$(P)) THEN IF J > 0 THEN R$(J-1) = R$(J-1)+TS$ : R$(P) = "-" : TS$ = ""
320 NEXT J
330 NEXT I
340 T$ = R$(0)
350 FOR I = 1 TO N
360 T$ = T$+","+R$(I)
370 NEXT I
380 PRINT S$;" = ";T$
390 ERASE R$
400 RETURN