irb(main):019:0> while b > 0.43 do
irb(main):020:1* c += 1
irb(main):021:1> b = -1 * (0.042 * a - a)
irb(main):022:1> puts b
irb(main):023:1> puts c
irb(main):024:1> a = b
irb(main):025:1> end
1.437
1
1.376646
2
1.318826868
3
1.263436139544
4
1.21037182168315
5
1.15953620517246
6
1.11083568455522
7
1.0641805858039
8
1.01948500120013
9
0.976666631149728
10
0.935646632641439
11
0.896349474070499
12
0.858702796159538
13
0.822637278720837
14
0.788086513014562
15
0.754986879467951
16
0.723277430530297
17
0.692899778448024
18
0.663797987753207
19
0.635918472267572
20
0.609209896432334
21
0.583623080782176
22
0.559110911389325
23
0.535628253110973
24
0.513131866480312
25
0.491580328088139
26
0.470933954308437
27
0.451154728227483
28
0.432206229641929
29
0.414053567996968
30
=> nil