import java.io.*;

import java.util.*;

import java.text.*;

import java.math.*;

import java.util.regex.*;

public class Solution {

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int n = in.nextInt();

int m = in.nextInt();

int[] a = new int[n];

int count=0,flag;

for(int a_i=0; a_i < n; a_i++){

a[a_i] = in.nextInt();

}

int[] b = new int[m];

for(int b_i=0; b_i < m; b_i++){

b[b_i] = in.nextInt();

}

for(int i=a[n-1];i<=b[0];i++){

flag=1;

for(int j=0;j<n;j++){

if(i%a[j]!=0){

flag=0;

}

}

for(int j=0;j<m;j++){

if(b[j]%i!=0){

flag=0;

}

}

if(flag==1){

count++;

}

}

System.out.print(count);

}

}