#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:36777216")
using namespace std;
const int N = 1e4 + 7;
const int INF = 0x7fffffff;
const int MOD = 1e9 + 7;
const double EPS = 1e-8;
void Debug(int a[], int n) {
  for (int i = 1; i <= n; i++) {
    for (int j = 30; j >= 0; j--) printf("%d", a[i] >> j & 1);
    puts("");
  }
  puts("");
}
int pos[50];
void Gao(int a[], int n, vector<pair<int, int> > &vec) {
  int r = 1;
  for (int i = 30; i >= 0; i--) {
    if ((a[r] >> i & 1) == 0) {
      int pos = -1;
      for (int j = r; j <= n; j++)
        if (a[j] >> i & 1) {
          pos = j;
          break;
        }
      if (pos == -1) continue;
      swap(a[r], a[pos]);
      vec.push_back(make_pair(r, pos));
      vec.push_back(make_pair(pos, r));
      vec.push_back(make_pair(r, pos));
    }
    for (int j = 1; j <= n; j++)
      if ((a[j] >> i & 1) && j != r) {
        a[j] ^= a[r];
        vec.push_back(make_pair(j, r));
      }
    pos[r] = i;
    r++;
  }
}
int Lcp(int a, int b) {
  int tot = 0;
  for (int i = 30; i >= 0; i--) {
    if ((a >> i & 1) != (b >> i & 1)) break;
    tot++;
  }
  return tot;
}
bool Check(int a[], int b[], int n, vector<pair<int, int> > &vec) {
  int r = 1;
  for (int i = 1; i <= 30; i++) {
    if (a[i] == b[i]) continue;
    for (int j = i; j <= 30; j++) {
      if (Lcp(a[i] ^ a[j], b[i]) > Lcp(a[i], b[i]))
        a[i] ^= a[j], vec.push_back(make_pair(i, j));
    }
    if (a[i] != b[i]) return false;
  }
  return true;
}
int n, a[N], b[N];
vector<pair<int, int> > vec1, vec2;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (int i = 1; i <= n; i++) scanf("%d", &b[i]);
  vector<pair<int, int> > vec1, vec2;
  Gao(a, n, vec1);
  Gao(b, n, vec2);
  if (!Check(a, b, n, vec1)) {
    puts("-1");
  } else {
    for (int i = vec2.size() - 1; i >= 0; i--) vec1.push_back(vec2[i]);
    printf("%d\n", vec1.size());
    for (int i = 0; i < vec1.size(); i++)
      printf("%d %d\n", vec1[i].first, vec1[i].second);
  }
}
