package main import ( "bufio" "fmt" "math" "os" "sort" "strconv" ) var sc = bufio.NewScanner(os.Stdin) var wr = bufio.NewWriter(os.Stdout) func out(x ...interface{}) { fmt.Fprintln(wr, x...) } func getI() int { sc.Scan() i, e := strconv.Atoi(sc.Text()) if e != nil { panic(e) } return i } func getF() float64 { sc.Scan() i, e := strconv.ParseFloat(sc.Text(), 64) if e != nil { panic(e) } return i } func getInts(N int) []int { ret := make([]int, N) for i := 0; i < N; i++ { ret[i] = getI() } return ret } func getS() string { sc.Scan() return sc.Text() } // min, max, asub, absなど基本関数 func max(a, b int) int { if a > b { return a } return b } func min(a, b int) int { if a < b { return a } return b } // min for n entry func nmin(a ...int) int { ret := a[0] for _, e := range a { ret = min(ret, e) } return ret } // max for n entry func nmax(a ...int) int { ret := a[0] for _, e := range a { ret = max(ret, e) } return ret } func asub(a, b int) int { if a > b { return a - b } return b - a } func abs(a int) int { if a >= 0 { return a } return -a } func lowerBound(a []int, x int) int { idx := sort.Search(len(a), func(i int) bool { return a[i] >= x }) return idx } func upperBound(a []int, x int) int { idx := sort.Search(len(a), func(i int) bool { return a[i] > x }) return idx } func rec(n, tgl int, p float64) float64 { if n == N { return 1 } ret := 0.0 ret = p/2.0 + (1-p)/3.0 nextP := 0.0 if tgl == 0 { nextP = math.Min(1.0, p+q) tgl = 1 } else { nextP = math.Max(0.0, p-q) tgl = 0 } r := rec(n+1, tgl, nextP) ret += p*r/2.0 + (1-p)*r/3.0 return ret } var p0, q float64 var N = 1000000 func main() { defer wr.Flush() sc.Split(bufio.ScanWords) sc.Buffer([]byte{}, 1000000) // this template is new version. // use getI(), getS(), getInts(), getF() p0, q = getF()/100.0, getF()/100.0 ret := rec(0, 1, p0)/3.0 + 1/3.0 out(ret) }