10 PRINT FRE(0)     
20 GOSUB 100     
30 GOTO 10
100 FOR i=1 TO 1000:NEXT:a$=str$(21):RETURN 
100 FOR i=1 TO 1000:NEXT:a$=str$(21):k=FRE(""):RETURN 



10 PRINT FRE(0)     
20 GOSUB 100     
30 GOTO 10
100 a$=str$(21):RETURN 