10 DIM S(5)
 20 LET P=1
 30 INPUT E$
 40 LET I=0
 50 LET I=I+1
 60 IF E$(I)=" " THEN GOTO 110
 70 IF I<LEN E$ THEN GOTO 50
 80 LET W$=E$
 90 GOSUB 150
100 STOP
110 LET W$=E$( TO I-1)
120 LET E$=E$(I+1 TO )
130 GOSUB 150
140 GOTO 40
150 IF W$="+" OR W$="-" OR W$="*" OR W$="/" OR W$="**" THEN GOTO 250
160 LET S(P)=VAL W$
170 LET P=P+1
180 PRINT W$;
190 PRINT ":";
200 FOR I=P-1 TO 1 STEP -1
210 PRINT " ";S(I);
220 NEXT I
230 PRINT
240 RETURN
250 IF W$="**" THEN LET S(P-2)=ABS S(P-2)
260 LET S(P-2)=VAL (STR$ S(P-2)+W$+STR$ S(P-1))
270 LET P=P-1
280 GOTO 180