#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pint=pair<int,int>;
#define rep(i,n) for(int i=0;i<(n);++i)
template<typename T>
void chmax(T& a,T b){if(a<b){a=b;};}
template<typename T>
void chmin(T& a,T b){if(a>b){a=b;};}
const int inf=1e9;

int main(){
  int n,m;cin>>n>>m;
  vector<int> u(n),d(m);
  rep(i,n)cin>>u[i];
  rep(i,m)cin>>d[i];
  vector<bool> dp(200000+1);
  rep(i,n)dp[u[i]]=true;
  rep(i,m)for(int j=200000-d[i];j>=0;--j)if(dp[j]){
    dp[j+d[i]]=true;
  }
  int ans=0;
  rep(i,200000+1)ans+=dp[i];
  cout<<ans<<endl;
}