IMPLICIT REAL(A-Z)
	INTEGER IDIGIT
	WRITE(1,1000)
1000	FORMAT('0LUNAR LANDER PROGRAM'/'$DO YOU NEED INSTRUCTIONS (Y/N)?')
	READ(1,1100) IANS
1100	FORMAT(A1)
	IF (IANS.NE.1HY) GO TO 250
	WRITE(1,1200)
1200	FORMAT('0INPUT FUEL RATE TO BE USED FOR THE NEXT 10 SECOND',
     1 /' INTERVAL.  IT CAN BE ZERO OR ANY VALUE BETWEEN 8 AND 200',
     2 /' LBS/SECOND.  A NEGATIVE VALUE WILL IMPLODE THE BOOSTER',
     3 /' AND ABORT THE MISSION.  CTRL-Z WILL TERMINAL THE PROGRAM.',
     4 /' STATUS AT THE END OF EACH 10 SECOND INTERVAL WILL BE',
     5 /' PRINTED AT THE TERMINAL.',
     6 /'0TOTAL LANDER WEIGHT (INCLUDING 16000 LBS OF FUEL)',
     7 /' IS 32500 LBS.',
     8 /'0GOOD LUCK!!')
250	L=0.
	A=120.
	V=1.
	M=32500.
	N=16500.
320	G=.001
	Z=1.8
	WRITE(1,2500)
2500	FORMAT('0TIME   HEIGHT     VELOCITY    FUEL LEFT  FUEL RATE')
350	IF (A.LT.1.) GO TO 355
C	   HIGH ALTITUDE PRINT OUT
	V2=V*3600.
	M2=M-N
	WRITE(1,3000) L,A,V2,M2,K
3000	FORMAT('$'F4.0,F8.1,' MI',F8.1,' MPH',F8.0,' LBS',F7.1,' LB/S'5X)
	GO TO 360
C	   LOW ALTITUDE PRINT OUT
355	V2=V*5280.
	M2=M-N
	A2=A*5280.
	WRITE(1,3500) L,A2,V2,M2,K
3500	FORMAT('$'F4.0,F8.1,' FT',F8.1,' FT/S',F7.0,' LBS',F7.1,' LB/S'5X)
C	   READ NEXT FUEL RATE
360	READ(1,5000,ERR=360,END=9999) K
5000	FORMAT(F10.0)
	T=10.
	IF (K.LT.0.) GO TO 250
	IF (K.EQ.0.) GO TO 470
	IF (K.LT.8.) GO TO 430
	IF (K.LE.200.) GO TO 470
430	WRITE(1,6000) K
6000	FORMAT('0',E15.5,' NOT POSSIBLE')
	GO TO 360
470	IF (M.LE.N) GO TO 590
	IF (T.LT.001) GO TO 350
	S=T
	IF (N+S*K.GT.M) S=(M-N)/J
	IO=1
	GO TO 1080
540	IF (I.LE.0.) GO TO 950
	IF (V.LE.0.) GO TO 570
	IF (J.LT.0.) GO TO 990
570	IO=1
	GO TO 880
C	   OUT OF FUEL
590	WRITE(1,7000) L
7000	FORMAT('0FUEL OUT AT ',E15.5,' SECONDS')
	S=(-V+SQRT(V*V+2.*A*G))/G
	V=V+G*S
	L=L+S
C	   ON THE MOON
630	WRITE(1,8000) L
8000	FORMAT('0ON THE MOON AT ',E15.5,' SECONDS')
	W=3600.*V
	WRITE(1,9000) W
9000	FORMAT('0IMPACT VELOCITY  OF 'E15.5,' MPH')
	X=AINT(M-N)
	WRITE(1,9100) X
9100	FORMAT('0FUEL LEFT = ',E15.5,' LBS')
	IF (W.GE.1.) GO TO 700
	WRITE(1,9200)
9200	FORMAT('0PERFECT LANDING! CONGRATULATIONS, COMMANDER!')
	GO TO 250
700	IF (W.GE.10.) GO TO 730
	WRITE(1,9300)
9300	FORMAT('0VERY GOOD LANDING, NOT PERFECT YET.')
	GO TO 250
730	IF (W.GE.25.) GO TO 760
	WRITE(1,9400)
9400	FORMAT('0FAIR LANDING, NO CRAFT DAMAGE.')
	GO TO 250
760	IF (W.GE.60.) GO TO 790
	WRITE(1,9500)
9500	FORMAT('0CRAFT DAMAGE -- BETTER LUCK NEXT TIME.')
	GO TO 250
790	X=.277*W
	IDIGIT=0
	IF (X.LT.1000.) IDIGIT=1
	IF (X.LT.100.) IDIGIT=2
	WRITE(1,9600) X
9600	FORMAT('0YOU HAVE JUST CREATED A NEW LUNAR CRATER ',
     + F5.<IDIGIT>,' FEET DEEP')
	GO TO 250
C
880	L=L+S
	T=T-S
	M=M-S*K
	A=I
	V=J
	IF (IO.EQ.1.) GO TO 470
	IF (IO.EQ.3.) GO TO 1050
950	IF (S.LT..005) GO TO 630
	S=2.*A/(V+SQRT(V*V+2.*A*(G-Z*K/M)))
	IO=2
	GO TO 1080
990	W=(1.-M*G/(Z*K))/2.
	S=M*V/(Z*K*(W+SQRT(W*W+V/Z)))+.05
	IO=3
	GO TO 1080
1030	IF (I.LE.0.) GO TO 950
	GO TO 880
1050	IF (J.GE.0.) GO TO 470
	IF (V.LE.0.) GO TO 470
	GO TO 990
1080	Q=S*K/M
	IF (Q.LT..000001) GO TO 1150
	J=V+G*S+Z*(-Q-Q**2/2.-Q**3/3.-Q**4/4.-Q**5/5.)
	I=A-G*S*S/2.-V*S+Z*S*(Q/2.+Q**2/6.+Q**3/12.+Q**4/20.+Q**5/30.)
1120	IF (IO.EQ.1.) GO TO 540
	IF (IO.EQ.2.) GO TO 880
	IF (IO.EQ.3.) GO TO 1030
1150	J=V+G*S
	I=A-G*S*S/2.-V*S
	GO TO 1120
9999	STOP
	END