#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int v, w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

double P0, P1, P2;

double f(int n, int k, vector<vector<double> >& memo) {
	if (memo[n][k] >= 0) return memo[n][k];
	if (k == 0) return memo[n][k] = n;
	double ans = 0;
	for (int S = 0; S < (1 << n); S++) {
		double p = 1; int x = 0;
		vector<int> v;
		for (int i = 0; i < n; i++) {
			double unko = (i == 0 || i == n - 1 ? P1 : P2);
			if (n == 1) unko = P0;
			if ((S >> i) & 1) {
				p *= 1 - unko;
				x++;
			}
			else {
				p *= unko;
				if (x) {
					v.push_back(x);
					x = 0;
				}
			}
		}
		if (x) v.push_back(x);
		double sum = 0;
		for (int j = 0; j < v.size(); j++)
			sum += f(v[j], k - 1, memo);
		ans += p * sum;
	}
	return memo[n][k] = ans;
}

int main() {
	int A; cin >> A;
	cin >> P0 >> P1 >> P2;
	P0 /= 100; P1 /= 100; P2 /= 100;
	vector<vector<double> > memo(15, vector<double>(80, -1));
	printf("%.10f\n", f(14, 80 - A, memo) * 2);
}