#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:60777216")
using namespace std;
int n;
int tx[11111];
int x[11111];
int y[11111];
int ty[11111];
int base[33];
bool u[11111];
bool uy[11111];
bool check(vector<pair<int, int> > v) {
  for (int i = (0); i < (v.size()); i++) {
    tx[v[i].first] ^= tx[v[i].second];
  }
  for (int i = (0); i < (n); i++)
    if (tx[i] != ty[i]) {
      puts("FUCK");
      while (1)
        ;
      return false;
    }
  return true;
}
int main() {
  cin >> n;
  for (int i = (0); i < (n); i++) scanf("%d", x + i);
  for (int i = (0); i < (n); i++) scanf("%d", y + i);
  memset(base, -1, sizeof base);
  memset(u, false, sizeof u);
  memset(uy, false, sizeof uy);
  for (int i = (0); i < (n); i++) tx[i] = x[i];
  for (int i = (0); i < (n); i++) ty[i] = y[i];
  vector<pair<int, int> > v;
  for (int bit = 0; bit < 30; bit++) {
    for (int i = (0); i < (n); i++) {
      if ((x[i] & (1 << bit)) && !u[i]) {
        u[i] = true;
        base[bit] = i;
        for (int j = (0); j < (n); j++)
          if (j != i)
            if (x[j] & (1 << bit)) {
              x[j] ^= x[i];
              v.push_back(pair<int, int>(j, i));
            }
        break;
      }
    }
  }
  bool good = true;
  for (int i = (0); i < (n); i++)
    if (!u[i]) {
      while (x[i])
        ;
      for (int j = (0); j < (30); j++)
        if (base[j] != -1) {
          if (y[i] & (1 << j)) {
            x[i] ^= x[base[j]];
            v.push_back(pair<int, int>(i, base[j]));
          }
        }
      if (x[i] != y[i]) {
        good = false;
        break;
      }
    }
  if (good) {
    vector<int> pos;
    for (int i = (0); i < (n); i++)
      if (u[i]) pos.push_back(i);
    vector<pair<int, int> > inv;
    for (int bit = 0; bit < 30; bit++) {
      for (int i = (0); i < (pos.size()); i++) {
        if ((y[pos[i]] & (1 << bit)) && !uy[pos[i]]) {
          uy[pos[i]] = true;
          for (int j = (0); j < (pos.size()); j++)
            if (j != i)
              if (y[pos[j]] & (1 << bit)) {
                y[pos[j]] ^= y[pos[i]];
                inv.push_back(pair<int, int>(pos[j], pos[i]));
              }
          break;
        }
      }
    }
    for (int i = (0); i < (pos.size()); i++) {
      if (y[pos[i]] == 0) continue;
      bool f = 0;
      for (int bit = (0); bit < (30); bit++)
        if (base[bit] != -1 && (y[pos[i]] & (1 << bit))) {
          f = 1;
          if (base[bit] != pos[i]) {
            for (int bit2 = (0); bit2 < (30); bit2++)
              if (base[bit2] == pos[i]) {
                v.push_back(pair<int, int>(pos[i], base[bit]));
                v.push_back(pair<int, int>(base[bit], pos[i]));
                v.push_back(pair<int, int>(pos[i], base[bit]));
                swap(x[pos[i]], x[base[bit]]);
                swap(base[bit], base[bit2]);
                break;
              }
          }
          for (int bit2 = (0); bit2 < (30); bit2++)
            if (base[bit2] != -1 && ((y[pos[i]] ^ x[pos[i]]) & (1 << bit2))) {
              x[pos[i]] ^= x[base[bit2]];
              v.push_back(pair<int, int>(pos[i], base[bit2]));
            }
          break;
        }
      if (!f) {
        good = 0;
        break;
      }
      if (x[pos[i]] != y[pos[i]]) {
        good = 0;
        break;
      }
    }
    for (int i = (0); i < (pos.size()); i++) {
      if (y[pos[i]]) continue;
      inv.push_back(pair<int, int>(pos[i], pos[i]));
    }
    reverse(inv.begin(), inv.end());
    for (int i = (0); i < (inv.size()); i++) {
      v.push_back(inv[i]);
    }
  }
  if (!good) {
    puts("-1");
  } else {
    cout << v.size() << endl;
    for (int i = (0); i < (v.size()); i++)
      printf("%d %d\n", v[i].first + 1, v[i].second + 1);
  }
  return 0;
}
