#include<bits/stdc++.h>
using namespace std;
int n,m,a[1005],b[1005],mapp[1005][1005],vis[1005][1005],sum;
int ds[3]={0,1,0},dy[3]={0,0,1};
void dfs(int x,int y){
    for (int i=1;i<=2;i++){
        int xx=x+ds[i],yy=y+dy[i];
        if (xx>=1&&xx<=n&&yy>=1&&yy<=m&&vis[xx][yy]==0&&mapp[xx][yy]==0){
            vis[xx][yy]=1;
            if(yy==m) sum++;
            dfs(xx,yy);
        }
    }
}
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 i=1;i<=m;i++) cin>>b[i];
    for (int i=1;i<=n;i++){
        for (int j=1;j<=m;j++){
            if(a[i]+b[j]<0) mapp[i][j]=1;
        }
    }
    for (int i=1;i<=n;i++){
        if (mapp[i][1]!=1) dfs(i,1);
        memset(vis,0,sizeof(vis));
    }
    cout<<sum;
    return 0;
}
/* * .
* . .
. . .*/