#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 10;
int n, cnt, A[MAXN], B[MAXN], pos[MAXN];
vector<pair<int, int> > Ra, Rb;
void lucky() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &A[i]);
  for (int i = 1; i <= n; i++) scanf("%d", &B[i]);
}
void Xor(int *A, vector<pair<int, int> > &R, int x, int y) {
  A[x] ^= A[y], R.push_back(pair<int, int>(x, y));
}
void getBase(int *A, vector<pair<int, int> > &R) {
  for (int i = 30, j, p = 1; i >= 0; i--) {
    for (j = p; j <= n && !(A[j] & (1 << i)); j++)
      ;
    if (j > n) continue;
    if (j != p) Xor(A, R, p, j), Xor(A, R, j, p), Xor(A, R, p, j);
    for (j = p + 1; j <= n; j++)
      if (A[j] & (1 << i)) Xor(A, R, j, p);
    p++;
  }
}
int main() {
  lucky();
  getBase(A, Ra), getBase(B, Rb);
  for (int i = 1; cnt++, i <= n && A[i]; i++)
    for (int j = 30; j >= 0; j--)
      if (A[i] & (1 << j)) {
        pos[i] = j;
        break;
      }
  for (int i = 1; i <= cnt; i++)
    for (int j = i; j <= cnt; j++)
      if ((A[i] ^ B[i]) & (1 << pos[j])) Xor(A, Ra, i, j);
  for (int i = 1; i <= n; i++)
    if (A[i] != B[i]) printf("-1\n"), exit(0);
  printf("%d\n", (int)(Ra.size() + Rb.size()));
  for (int i = 0; i < (int)Ra.size(); i++)
    printf("%d %d\n", Ra[i].first, Ra[i].second);
  for (int i = Rb.size() - 1; i >= 0; i--)
    printf("%d %d\n", Rb[i].first, Rb[i].second);
  return 0;
}
