#include <bits/stdc++.h>
using namespace std;
int getint() {
  int x = 0;
  char c = getchar();
  while (c < '0' || c > '9') c = getchar();
  while (c >= '0' && c <= '9') x *= 10, x += (c - '0'), c = getchar();
  return x;
}
vector<pair<int, int> > v[2];
int n, a[2][10010];
void XOR(int i, int j, int idx) {
  v[idx].push_back(make_pair(i, j));
  a[idx][i] ^= a[idx][j];
}
void init() {
  n = getint();
  for (int j = 0; j < 2; j++)
    for (int i = 0; i < n; i++) a[j][i] = getint();
}
void Gauss(int idx) {
  int pre = 0;
  for (int i = 30; i >= 0; i--)
    for (int j = pre; j < n; j++)
      if (a[idx][j] & (1 << i)) {
        if (j != pre) {
          XOR(j, pre, idx);
          XOR(pre, j, idx);
          XOR(j, pre, idx);
        }
        for (int k = 0; k < n; k++)
          if (k != pre && (a[idx][k] & (1 << i))) XOR(k, pre, idx);
        pre++;
        break;
      }
}
void solve() {
  for (int i = 0; i < 2; i++) Gauss(i);
  for (int i = 0; i < n; i++)
    if (a[0][i]) {
      int bs = (1 << 30);
      while ((a[0][i] & bs) == 0) bs >>= 1;
      for (int j = 0; j <= 30 && j < n; j++)
        if ((a[0][j] ^ a[1][j]) & bs) XOR(j, i, 0);
    } else
      break;
  for (int i = 0; i < n; i++)
    if (a[0][i] != a[1][i]) {
      puts("-1");
      return;
    }
  printf("%d\n", (int)v[0].size() + (int)v[1].size());
  for (int i = 0; i < (int)v[0].size(); i++)
    printf("%d %d\n", v[0][i].first + 1, v[0][i].second + 1);
  for (int i = (int)v[1].size() - 1; i >= 0; i--)
    printf("%d %d\n", v[1][i].first + 1, v[1][i].second + 1);
}
int main() {
  init();
  solve();
}
