#include <iostream>
#include <bits/stdc++.h>
using namespace std;
const int maxn = 105;
const double EPS = 1e-7;
int classrooms, teachers;
double c[maxn], t[maxn];
int max_taken_with_a_teacher[maxn][maxn];
bool is_A_less_than_B(double a, double b) {
    if(a < b) {
        return true;
    }
    if(fabs(a - b) < EPS) {
        return true;
    }
    return false;
}
int dp[maxn][1 << 14];
bool rec(int at, int visited, double & mid) {
    if(at == classrooms) {
        return true;
    }
    if(__builtin_popcount(visited) == teachers) {
        return false;
    }
    if(dp[at][visited] != -1) {
        return dp[at][visited];
    }
    for(int i = 0; i < teachers; i++) {
        if(!(visited & (1 << i))) {
            if(rec(max_taken_with_a_teacher[i][at], (visited | (1 << i)), mid)) {
                return dp[at][visited] = true;
            }
        }
    }
    return dp[at][visited] = false;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin >> classrooms >> teachers;
    
    for(int i = 0; i < classrooms; i++) {
        cin >> c[i];
    }
    for(int i = 0; i < teachers; i++) {
        cin >> t[i];
    }
    double L = 0.0, R = 2000000.0;
    while(fabs(L - R) > EPS) {
        double mid = L + (R - L) / 2.0;
        for(int i = 0; i < teachers; i++) {
            for(int j = 0; j < classrooms; j++) {
                double sum = 0.0;
                int k = j;
                while(k < classrooms and is_A_less_than_B(sum, mid)) {
                    if(is_A_less_than_B(sum + (c[k] / t[i]), mid)) {
                        sum += (c[k] / t[i]);
                        k++;
                    }
                    else {
                        break;
                    }
                }
                max_taken_with_a_teacher[i][j] = k;
            }
        }
        memset(dp, -1, sizeof dp);
        if(rec(0, 0, mid)) {
            R = mid;
        }
        else {
            L = mid;
        }
    }
    printf("%.6lf\n", L);
    return 0;
}