#include <iostream>
#include <assert.h>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

double P[3];
double dp[22][15];

double solve(int depth, int num) {

    if(depth == 0) { return num; }

    double& ret = dp[depth][num];
    if(ret >= 0) { return ret; }

    if(num == 1) { return ret = solve(depth-1, 1)*(1.0-P[0]); }

    ret = 0.;
    rep(S, 1<<num) {
        double prob = 1.0;
        rep(i, num) {
            double bad = (i==0||i==num-1) ? P[1] : P[2];
            if(S && (1<<i)) { prob *= 1.0-bad;  }
            else            { prob *= bad;      }
        }

        int next_num = 0;
        rep(i, num) {
            if(S & (1<<i)) {
                next_num ++;
            }
            else {
                if(next_num) {
                    ret += solve(depth-1, next_num) * prob;
                }
                next_num = 0;
            }
        }
        if(next_num) {
            ret += solve(depth-1, next_num) * prob;
        }
    }
    return ret;
}

int main() {
    int year; cin >> year;
    rep(i, 3) { cin >> P[i]; P[i] /= 100.0; }
    rep(i, 22) rep(j, 15) { dp[i][j] = -1.0; }
    printf("%.9lf\n", solve(80-year, 14) * 2.0);
    return 0;
}