10 LET A = 0
20 LET B = 1
30 PRINT "Which F_n do you want?"
40 INPUT N
50 IF N = 0 THEN GOTO 140
60 IF N = 1 THEN GOTO 120
70 LET C = B + A
80 LET A = B
90 LET B = C
100 LET N = N - 1
110 GOTO 60
120 PRINT B
130 END
140 PRINT 0
150 END