#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool isLeap(T y) {
  return (y % 400 == 0) || (y % 100 ? y % 4 == 0 : false);
}
template <class T>
inline T gcd(T a, T b) {
  return (b) == 0 ? (a) : gcd((b), ((a) % (b)));
}
template <class T>
inline T lcm(T a, T b) {
  return ((a) / gcd((a), (b)) * (b));
}
template <class T>
inline T BigMod(T Base, T power, T M = 1000000007) {
  if (power == 0) return 1;
  if (power & 1)
    return ((Base % M) * (BigMod(Base, power - 1, M) % M)) % M;
  else {
    T y = BigMod(Base, power / 2, M) % M;
    return (y * y) % M;
  }
}
template <class T>
inline T ModInv(T A, T M = 1000000007) {
  return BigMod(A, M - 2, M);
}
int fx[] = {-1, +0, +1, +0, +1, +1, -1, -1, +0};
int fy[] = {+0, -1, +0, +1, +1, -1, +1, -1, +0};
int day[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int n, m;
long long arr1[300005], arr2[300005];
vector<int> v1, v2;
int l, r;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n;
  for (int i = 0; i < n; i++) cin >> arr1[i];
  cin >> m;
  for (int i = 0; i < m; i++) cin >> arr2[i];
  int flag = 0;
  int ans = 0;
  while (l < n || r < m) {
    if (l == n && r < m || l < n && r == m) {
      flag = 1;
      break;
    }
    if (arr1[l] == arr2[r]) {
      ans++;
      l++;
      r++;
    } else {
      long long cum = arr1[l], pum = arr2[r];
      while (cum != pum) {
        if (cum < pum) {
          if (l == n - 1) {
            flag = 1;
            break;
          }
          l++;
          cum += arr1[l];
        } else {
          if (r == m - 1) {
            flag = 1;
            break;
          }
          r++;
          pum += arr2[r];
        }
      }
      if (cum == pum) {
        ans++;
        l++;
        r++;
      } else {
        flag = 1;
        break;
      }
    }
    if (flag) break;
  }
  if (flag)
    cout << -1;
  else
    cout << ans;
  return 0;
}
