#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
#define rep(i, n) REP(i, 0, n)
#define REP(i, s, e) for (ll i = (s); i < (ll)(e); i++)
#define repr(i, n) REPR(i, n, 0)
#define REPR(i, s, e) for (ll i = (ll)(s - 1); i >= (ll)(e); i--)
#define all(r) r.begin(), r.end()
#define rall(r) r.rbegin(), r.rend()

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;

template <typename T, typename U>
bool chmax(T& a, const U& b) {
    if (a >= b) return false;
    a = b;
    return true;
}
template <typename T, typename U>
bool chmin(T& a, const U& b) {
    if (a <= b) return false;
    a = b;
    return true;
}

void yes_no(bool f, string yes = "Yes", string no = "No") {
    cout << (f ? yes : no) << "\n";
}

void solve() {
    int a;
    cin >> a;
    a = 80 - a;
    using D = double;
    vector<D> p(3);
    rep(i, 3) cin >> p[i], p[i] /= 100.0;
    const int m = 14;
    vector dp(a + 1, vector(m + 1, (D)0));
    vector used(a + 1, vector(m + 1, (int)0));
    auto dfs = [&](auto self, int x, int len) -> D {
        if (used[x][len]) return dp[x][len];
        used[x][len] = 1;
        auto& ret = dp[x][len];
        if (x == 0) return ret = len;
        if (len == 0) return ret = 0;
        if (len == 1) {
            D t = p[0];
            return ret = self(self, x - 1, 1) * (1 - t);
        } else {
            rep(mask, 1 << len) {
                D t = 1;
                vi v;
                int cnt = 0;
                rep(i, len) {
                    if (mask & (1 << i)) {
                        if (i == 0 || i + 1 == len) t *= p[1];
                        else t *= p[2];
                        if (cnt > 0) v.emplace_back(cnt);
                        cnt = 0;
                    } else {
                        if (i == 0 || i + 1 == len) t *= (1 - p[1]);
                        else t *= (1 - p[2]);
                        ++cnt;
                    }
                }
                if (cnt > 0) v.emplace_back(cnt);
                rep(i, v.size()) ret += self(self, x - 1, v[i]) * t;
            }
        }
        return ret;
    };
    D ans = dfs(dfs, a, m) * 2;
    cout << fixed << setprecision(15);
    cout << ans << "\n";
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int t = 1;
    // multi-testcase
    // cin >> t;
    rep(ti, t) solve();
    return 0;
}