#include <bits/stdc++.h>
inline int read() {
  int ret;
  scanf("%d", &ret);
  return ret;
}
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
using namespace std;
int x[11111], y[11111];
int n;
vector<pair<int, int> > ans0, ans1;
int prework(int x[], vector<pair<int, int> > &ans) {
  int start = 1;
  for (int i = 30; i >= 0; i--) {
    for (int j = start; j <= n; j++) {
      if ((x[j] >> i) & 1) {
        swap(x[start], x[j]);
        if (start != j) {
          ans.push_back(make_pair(j, start));
          ans.push_back(make_pair(start, j));
          ans.push_back(make_pair(j, start));
        }
        for (int k = 1; k <= int(n); k++) {
          if (k != start && ((x[k] >> i) & 1)) {
            x[k] ^= x[start];
            ans.push_back(make_pair(k, start));
          }
        }
        start++;
        break;
      }
    }
  }
  return start - 1;
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= int(n); i++) scanf("%d", &x[i]);
  for (int j = 1; j <= int(n); j++) scanf("%d", &y[j]);
  int l1 = prework(x, ans0);
  int l2 = prework(y, ans1);
  for (int i = 1; i <= int(l1); i++) {
    int c = 30;
    while (((x[i] >> c) & 1) == 0) c--;
    for (int j = 1; j <= int(l1); j++) {
      if (((y[j] >> c) & 1) != ((x[j] >> c) & 1)) {
        ans0.push_back(make_pair(j, i));
        x[j] ^= x[i];
      }
    }
  }
  bool YES = true;
  for (int i = 1; i <= int(l1); i++)
    if (x[i] != y[i]) YES = false;
  if (l1 < l2) YES = false;
  if (YES == false) {
    puts("-1");
    return 0;
  }
  printf("%d\n", ans0.size() + ans1.size());
  for (int i = 0; i < int(ans0.size()); i++)
    printf("%d %d\n", ans0[i].first, ans0[i].second);
  for (int i = 0; i < int(ans1.size()); i++)
    printf("%d %d\n", ans1[ans1.size() - i - 1].first,
           ans1[ans1.size() - i - 1].second);
  return 0;
}
