from itertools import *
from bisect import *
from collections import *
from heapq import *
import sys

sys.setrecursionlimit(10 ** 6)

def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def SI(): return sys.stdin.readline()[:-1]
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
int1 = lambda x: int(x) - 1
def MI1(): return map(int1, sys.stdin.readline().split())
def LI1(): return list(map(int1, sys.stdin.readline().split()))
p2D = lambda x: print(*x, sep="\n")
dij = [(1, 0), (0, 1), (-1, 0), (0, -1)]

def main():
    roop=1000
    p0,q=MI()
    if q==0:
        fp=(p0+200)/(400-p0)
        ans=(1+fp)/3
        print(ans)
        exit()
    pp=set()
    for np in range(p0,100,q):pp.add(np)
    for np in range(p0-q,0,-q):pp.add(np)
    for np in range(0,100,q):pp.add(np)
    for np in range(100,0,-q):pp.add(np)
    dp=[0.5]*101
    for _ in range(roop):
        for p in pp:dp[p]=(p+200)/600+p*dp[max(0,p-q)]/200+(100-p)*dp[min(100,p+q)]/300
    ans=(1+dp[p0])/3
    print(ans)

main()