#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 2005
ll a[MAXN],b[MAXN];
ll used[MAXN][MAXN];
ll ans,n,m;
void dfs(ll x,ll y){
    if(used[x][y])return;
//    cout<<x<<" "<<y<<endl;
    used[x][y]=1;
    if(y==m){
        ans++;
        return;
    }
    if(a[x+1]+b[y]>=0&&x+1<=n)dfs(x+1,y);
    if(a[x]+b[y+1]>=0&&y+1<=m)dfs(x,y+1);
}
int main(){
    freopen("expansion.in","r",stdin);
    freopen("expansion.out","w",stdout);
    cin>>n>>m;
    for(int i=1;i<=n;i++)cin>>a[i];
    for(int j=1;j<=m;j++)cin>>b[j];
    for(int i=1;i<=n;i++){
        if(a[i]+b[1]<0)continue;
        dfs(i,1);
        memset(used,0,sizeof(used));
    }
    cout<<ans;
    return 0;
}