#include <bits/stdc++.h>
using namespace std;
typedef vector<int> VI;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))

int A,P0,P1,P2;
double p0,p1,p2;
double memo[111][111];

double dfs(int l, int n){
    if(n == 0) return l;
    if(memo[l][n] == memo[l][n]) return memo[l][n];
    if(l == 1) return memo[l][n] = (1-p0)*dfs(l,n-1);
    double res = 0;
    for(int i=1; i<=l; i++){
        REP(j,l-i+1){
            double p = 1;
            for(int k = j-1; k <= j+i; k++){
                if(k < 0 || k >= l) continue;
                double q = (k==0 || k==l-1) ? p1 : p2;
                if(k > j-1 && k < j+i) q = 1 - q;
                p *= q;
            }
            res += p * dfs(i, n-1);
        }
    }
    return memo[l][n] = res;
}

int main(){
    cin >> A >> P0 >> P1 >> P2;
    p0 = P0/100.0, p1 = P1/100.0, p2 = P2/100.0;
    memset(memo, -1, sizeof(memo));
    cout << fixed << setprecision(12) << dfs(14,80-A)*2 << endl;
    return 0;
}