#include <bits/stdc++.h>
using namespace std;
int n,m,xy[2][2]={{0,1},{1,0}},res;
long long b[310][2],a[310][310],mk[310][310];
struct node {
    int x,y;
};
void bfs (int x,int y) {
    queue<node>q;
    q.push((node){x,y});
    while (q.size()) {
        node t=q.front();
        q.pop();
        for (int i=0;i<2;i++) {
            int xx=t.x+xy[i][0];
            int yy=t.y+xy[i][1];
            if (xx>0&&xx<=n&&yy>0&&yy<=m&&a[xx][yy]>=0&&mk[xx][yy]==0) {
                mk[xx][yy]=1;
                if (yy==m) res++;
                q.push((node){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 >> b[i][0];
    for (int i=1;i<=m;i++) cin >> b[i][1];
    for (int i=1;i<=n;i++) {
        for (int j=1;j<=m;j++) {
            a[i][j]=b[i][0]+b[j][1];
        }
    }
    for (int i=1;i<=n;i++) {
        if (a[i][1]<0) continue;
        bfs(i,1);
        memset(mk,0,sizeof(mk));
    }
    cout << res <<endl;
    return 0;
}