//ドワンゴ　フィッシング　8020
//SYAKYO
//http://yukicoder.me/submissions/12291
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const double EPS = 1e-9;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

double memo[100][100];
int P[3];

double func(int y,int n){
	if(y == 0)return n;
	if(memo[y][n] >= 0)return memo[y][n];

	if(n == 1){
		memo[y][n] = (100-P[0])/100. * func(y-1,1);
	}else{
		memo[y][n] = 0;
		for(int mk=0;mk < (1<<n);mk++){
			double prob = 1;
			for(int i=0;i<n;i++){
				double bad;
				if(i==0 || i==n-1)
					bad = P[1] / 100.0;
				else
					bad = P[2] / 100.0;

				if(mk & (1<<i))
					prob *= 1-bad;
				else
					prob *= bad;
			}

			int left = 0;
			for(int i=0;i<n;i++){
				if(mk & (1<<i)){
					left++;
				}
				else{
					if(left > 0)
						memo[y][n] += prob * func(y-1,left);
					left = 0;
				}
			}
			if(left > 0)
				memo[y][n] += prob * func(y-1,left);
		}
	}
	return memo[y][n];

}

int main(void) {	
	int A;cin >> A;
	cin >> P[0] >> P[1] >> P[2];
	for(int i=0;i<100;i++)for(int j=0;j<100;j++)memo[i][j] = -1;
	cout << fixed << setprecision(10) << func(80-A, 14) * 2.<< endl;

	return 0;
}