import sys
read=sys.stdin.buffer.read
readline=sys.stdin.buffer.readline
readlines=sys.stdin.buffer.readlines

import numpy as np
p0, q=map(int, readline().split())
mat=np.zeros((101, 101), dtype=np.float64)
b=np.zeros(101, dtype=np.float64)
for p in range(101):
    p1=max(0, p-q)
    p2=min(100, p+q)
    mat[p][p1]-=p/200
    mat[p][p]+=1
    mat[p][p2]-=(100-p)/300
    b[p]=p/200+(100-p)/300
x=np.linalg.solve(mat, b)
print('{:.7f}'.format(1/3+1/3*x[p0]))