a = 80 - int(input())
p0,p1,p2 = map(int,input().split())
p0 /= 100
p1 /= 100
p2 /= 100

n = 15
A = [[0.0]*n for _ in range(2)]
A[1][1] = 1.0-p0
# A[i][j] = i 本連続の歯が 1 年後に持つ j 本連続の歯の期待値
for i in range(2,n):
    r = [0.0]*n
    for mask in range(1<<i):
        p = 1.0
        for j in range(i):
            if mask>>j&1:
                p *= 1-p1 if j == 0 or j == i-1 else 1-p2  
            else:
                p *= p1 if j == 0 or j == i-1 else p2
        cnt = 0
        for j in range(i+1):
            if mask>>j&1:
                cnt += 1
            else:
                r[cnt] += p
                cnt = 0
    A.append(r)

dp = list(range(n))
for _ in range(a):
    ndp = [0.0]*n
    for i in range(n):
        v = 0.0
        for j in range(n):
            v += A[i][j]*dp[j]
        ndp[i] = v
    dp = ndp

print(dp[14]*2)