#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5;
int n, a[N], b[N];
vector<pair<int, int> > ans1, ans2;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i++) {
    cin >> b[i];
  }
  for (int i = 1, j = 30; i <= n && j >= 0; j--) {
    for (int k = i; k <= n; k++) {
      if (a[k] & (1 << j)) {
        if (i == k) {
          break;
        }
        a[i] ^= a[k];
        ans1.push_back(make_pair(i, k));
        break;
      }
    }
    if ((a[i] & (1 << j)) == 0) {
      continue;
    }
    for (int k = 1; k <= n; k++) {
      if (k != i && (a[k] & (1 << j))) {
        a[k] ^= a[i];
        ans1.push_back(make_pair(k, i));
      }
    }
    i++;
  }
  for (int i = 1, j = 30; i <= n && j >= 0; j--) {
    for (int k = i; k <= n; k++) {
      if (b[k] & (1 << j)) {
        if (i == k) {
          break;
        }
        b[i] ^= b[k];
        ans2.push_back(make_pair(i, k));
        break;
      }
    }
    if ((b[i] & (1 << j)) == 0) {
      continue;
    }
    for (int k = 1; k <= n; k++) {
      if (k != i && (b[k] & (1 << j))) {
        b[k] ^= b[i];
        ans2.push_back(make_pair(k, i));
      }
    }
    i++;
  }
  for (int i = 1; i <= n; i++) {
    int x = a[i], y = b[i];
    for (int j = 30; j >= 0; j--) {
      if (((x ^ y) >> j) & 1) {
        for (int k = 1; k <= n; k++) {
          if ((a[k] >> j) & 1) {
            ans1.push_back(make_pair(i, k));
            x ^= a[k];
            break;
          }
        }
      }
    }
    if (x != y) {
      return cout << "-1", 0;
    }
  }
  cout << ans1.size() + ans2.size() << "\n";
  for (auto it : ans1) {
    cout << it.first << " " << it.second << "\n";
  }
  reverse(ans2.begin(), ans2.end());
  for (auto it : ans2) {
    cout << it.first << " " << it.second << "\n";
  }
}
