A=int(raw_input())
P0,P1,P2=map(int,raw_input().split())
dp=[[-1.0 for i in range(15)] for j in range(20)]

def rec(age, n):
    #print age-A,n
    if age == 80:
        return n
    elif n==0:
        return 0
    elif dp[age-A][n] >=0:
        return dp[age-A][n]
    elif n==1:
        dp[age-A][n]=rec(age+1,1)*(100-P0)/100.0
        return dp[age-A][n]
    ans = 0
    for m in range(1<<n):
        eLen = 0.0
        prob = 1.0
        nextN=0
        for l in range(n):
            if m&(1<<l)==0:
                if l == 0 or l == n-1:
                    prob *= P1/100.0
                else:
                    prob *= P2/100.0
                if nextN>0:
                    eLen += rec(age+1,nextN)
                    nextN=0
            else:
                if l==0 or l==n-1:
                    prob *= (100-P1)/100.0
                else:
                    prob *= (100-P2)/100.0
                nextN+=1
        if nextN>0:
            eLen += rec(age+1,nextN)
        ans += eLen*prob
    dp[age-A][n]=ans
    return dp[age-A][n]

print rec(A,14)*2