UVa_11242_Tour_de_France

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class UVa_11242_Tour_de_France {

	public static void main(String[] args) {
		
		int[] f_arr,r_arr;
		int i;
		int f,r,m;
		double temp,spreadmax,spread;
		Scanner in = new Scanner(System.in);
		f = in.nextInt();
		while(f!=0){
			f_arr= new int[f];
			r=in.nextInt();
			r_arr = new int[r];
			for(i=0 ; i<f;i++){
				f_arr[i]=in.nextInt();
			}
			for(i=0 ; i<f;i++){
				r_arr[i]=in.nextInt();
			}
			ArrayList<Double> list = new ArrayList<Double>(r*f);
			for(i=0;i<f;i++){
				for(int j = 0 ; j<r;j++){
					temp=r_arr[j]/f_arr[i];
					list.add(temp);
				//	System.out.print(temp+ " ");
				}
			}
			Collections.sort(list);
			m = 1;
			spreadmax=-1;
			spread=0;
			while (list.size() > m) {
				spread = list.get(m)/list.get(m-1);
				if(spread>spreadmax){
					spreadmax=spread;
				}
				m++;
			}
			System.out.println(spreadmax);
			f=in.nextInt();
		}
		in.close();
	}

}