#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int a[N], c[N];
/*
2 2
9 9
1 -1

参考答案：10
*/
int main() {
  int n, m;
  cin >> n >> m;
  int mx = -1e9;
  for (int i = 1; i <= n; i++) {
    cin >> c[i];
    mx = max(mx, c[i]);
  }
  for (int i = 1; i <= m; i++)
    cin >> a[i];

  for (int i = 1; i <= m;i++) { // 注意特殊情况，比如n=1,此时如果a[i]<0,那么就只能是减掉
    if (n == 1 || a[i] > 0)
      mx += a[i];
  }
  cout << mx << endl;

  return 0;
}