改进了一下，考虑到contribute每年涨4%。每年ROI=10.0%

	monrthly return =	0.00798502		yearly return =	1.100142
month	contribution	before gain	gain	after gain		V/Cont
1	1000	1000	7.99	1007.99		1.007985
2	1003.27	2011.26	16.06	2027.32		1.012003
3	1006.56	3033.88	24.23	3058.10		1.016038
4	1009.85	4067.96	32.48	4100.44		1.020089
5	1013.16	5113.60	40.83	5154.43		1.024158
6	1016.48	6170.91	49.27	6220.19		1.028245
7	1019.81	7239.99	57.81	7297.80		1.032348
8	1023.14	8320.95	66.44	8387.39		1.036469
9	1026.49	9413.88	75.17	9489.05		1.040607
10	1029.85	10518.91	83.99	10602.90		1.044763
11	1033.23	11636.13	92.91	11729.04		1.048936
12	1036.61	12765.65	101.93	12867.59		1.053127
13	1040.00	13907.59	111.05	14018.64		1.057335
14	1043.41	15062.05	120.27	15182.32		1.061562
15	1046.82	16229.15	129.59	16358.74		1.065806
16	1050.25	17408.99	139.01	17548.00		1.070069
17	1053.69	18601.69	148.53	18750.22		1.074349
18	1057.14	19807.36	158.16	19965.53		1.078648
19	1060.60	21026.13	167.89	21194.02		1.082964
20	1064.07	22258.09	177.73	22435.83		1.087299
21	1067.56	23503.38	187.67	23691.06		1.091653
22	1071.05	24762.11	197.73	24959.84		1.096025
23	1074.56	26034.39	207.89	26242.28		1.100415
24	1078.08	27320.36	218.15	27538.51		1.104824
25	1081.61	28620.12	228.53	28848.65		1.109252
26	1085.15	29933.80	239.02	30172.82		1.113698
27	1088.70	31261.52	249.62	31511.14		1.118164
28	1092.27	32603.41	260.34	32863.75		1.122648
29	1095.84	33959.59	271.17	34230.76		1.127152
30	1099.43	35330.19	282.11	35612.30		1.131674
31	1103.03	36715.33	293.17	37008.50		1.136216
32	1106.64	38115.14	304.35	38419.49		1.140777
33	1110.26	39529.75	315.65	39845.40		1.145357
34	1113.90	40959.30	327.06	41286.36		1.149957
35	1117.54	42403.90	338.60	42742.50		1.154577
36	1121.20	43863.70	350.25	44213.95		1.159216
37	1124.87	45338.83	362.03	45700.86		1.163875
38	1128.56	46829.42	373.93	47203.35		1.168553
39	1132.25	48335.60	385.96	48721.56		1.173252
40	1135.96	49857.52	398.11	50255.64		1.177970
41	1139.68	51395.31	410.39	51805.71		1.182709
42	1143.41	52949.12	422.80	53371.92		1.187468
43	1147.15	54519.07	435.34	54954.41		1.192247
44	1150.91	56105.31	448.00	56553.32		1.197046
45	1154.68	57707.99	460.80	58168.79		1.201866
46	1158.46	59327.25	473.73	59800.98		1.206706
47	1162.25	60963.23	486.79	61450.02		1.211567
48	1166.06	62616.08	499.99	63116.07		1.216449
49	1169.87	64285.94	513.32	64799.27		1.221352
50	1173.70	65972.97	526.80	66499.76		1.226275
51	1177.55	67677.31	540.40	68217.72		1.231220
52	1181.40	69399.12	554.15	69953.27		1.236185
53	1185.27	71138.54	568.04	71706.58		1.241172
54	1189.15	72895.73	582.07	73477.81		1.246180
55	1193.04	74670.85	596.25	75267.10		1.251209
56	1196.95	76464.05	610.57	77074.61		1.256260
57	1200.87	78275.48	625.03	78900.51		1.261332
58	1204.80	80105.31	639.64	80744.95		1.266427
59	1208.74	81953.70	654.40	82608.10		1.271542
60	1212.70	83820.80	669.31	84490.11		1.276680
61	1216.67	85706.78	684.37	86391.15		1.281840
62	1220.66	87611.81	699.58	88311.39		1.287021
63	1224.65	89536.04	714.95	90250.99		1.292225
64	1228.66	91479.65	730.47	92210.12		1.297451
65	1232.68	93442.80	746.14	94188.94		1.302700
66	1236.72	95425.66	761.98	96187.64		1.307971
67	1240.77	97428.41	777.97	98206.38		1.313264
68	1244.83	99451.21	794.12	100245.33		1.318580
69	1248.91	101494.23	810.43	102304.67		1.323919
70	1253.00	103557.66	826.91	104384.57		1.329281
71	1257.10	105641.67	843.55	106485.22		1.334666
72	1261.21	107746.43	860.36	108606.79		1.340073