#include <iostream>
#include <vector>
#include <cmath>
//#include <bits/stdc++.h>
#include <cstring>
using namespace std;
double c[105], t[105];
const double EPS = 1e-9;
int classrooms, teachers;

bool is_a_less_than_b(double a, double b) {
    if(a < b) {
        return true;
    }
    if((a - b) < EPS) {
        return true;
    }
    return false;
}
int max_right_with_a_person[15][101];
double cost[15][101];
int dp[101][1 << 15];
bool rec(int at, int visited, double &x) {
    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))) {
            int new_mask = (visited | (1 << i));
            if(is_a_less_than_b(cost[i][at], x) and rec(max_right_with_a_person[i][at], new_mask, x)) {
                return dp[at][visited] = true;
            }
        }
    }
    return dp[at][visited] = false;
}
int main() {
    cin >> classrooms >> teachers;
    for(int i = 0; i < classrooms; i++) {
        int o;
        cin >> o;
        c[i] = (double) o;
    }
    for(int i = 0; i < teachers; i++) {
        int o;
        cin >> o;
        t[i] = (double) o;
    }
    double L = 0.00;
    double R = 20000000.0;
    while(fabs(L - R) > EPS) {
        double x = L + (R - L) / 2.0;
        
        for(int i = 0; i < teachers; i++) {
            for(int j = 0; j < classrooms; j++) {
                int it = j;
                double p = 0.0;
                bool can = false;
                while(it < classrooms and is_a_less_than_b(p, x)) {
                    if (is_a_less_than_b(p + (c[it] / t[i]), x)){
                        p += (c[it] / t[i]);
                        it++;
                        can = true;
                    }
                    else {
                        break;
                    }
                }
                max_right_with_a_person[i][j] = it;
                cost[i][j] = p;
            }
        }
//        cout << x << endl;
        memset(dp, -1, sizeof dp);
        if(rec(0, 0, x)) {
            R = x;
        }
        else {
            L = x;
        }
    }
    printf("%.6f\n", L);
    return 0;
}