#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

const int X = 14;
int N;
double ps[3];
double powqs[X+1];
double memo[21][X+1][2];

double rec(int i, int j, bool first) {
	double &r = memo[i][j][first];
	if(r == r) return r;
	if(i == N) return r = j;
	if(j == 0) return r = 0;
	r = 0;
	rer(k, 0, j) {
		double p;
		int lk = !first + (j != 1), rk = (k != 1 && j != 1) + (k != j);
		int sk = (!first || k != 0) + (k != j - 1);
		if(k == 0) {
			p = 1;
		}else if(k == 1) {
			p = 1 - ps[lk];
		}else {
			p = (1 - ps[lk]) * powqs[k-2] * (1 - ps[rk]);
		}
		if(k != j)
			p *= ps[sk];
		r += p * (rec(i+1, k, true) + rec(i, k == j ? 0 : j - k - 1, false));
	}
	return r;
}

int main() {
	int A, P0, P1, P2;
	cin >> A >> P0 >> P1 >> P2;
	N = 80 - A;
	ps[0] = P0 / 100., ps[1] = P1 / 100., ps[2] = P2 / 100.;
	powqs[0] = 1;
	rep(i, X) powqs[i+1] = powqs[i] * (1 - ps[2]);
	mset(memo, -1);
	double ans = rec(0, X, true) * 2;
	printf("%.10f\n", ans);
	return 0;
}