5 ONERRORGOTO500
10 y=ABSx:p=0
15 IFy>100 THEN60
20 IFy<1.9 THEN50
30 FORi=18 TO1 STEP-1:p=i/(y+p):NEXT
40 p=EXP(-.5*y*y)/SQR(2*PI)/(y+p):GOTO60
50 p=(1+y*(.049867347+y*(.0211410061+y*(.0032776263+y*(.0000380036+y*(.0000488906+y*.000005383))))))^-16/2
60 IFx<0 THENp=1-p
80 y=p:RETURN
500 IFERR=1 THENCLS:ONERRORGOTO0
510 sr=1:RESUME80