#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define endl '\n'
const int N = 2e3 + 30;

int n;
int a[N], b[N], pos[N];

void solve() {
    cin >> n;
    for (int i = 1; i <= n; i ++) {
        cin >> a[i];
    }
    for (int i = 1; i <= n; i ++) {
        cin >> b[i];
        pos[b[i]] = i;
    }
    vector<pair<int, int>> ans;
    for (int now = n; now >= 1; now --) {
        int l = 1, r = 1;
        while (a[l] != now) l ++;
        r = pos[a[l]];
//      cout << now << ' ' << l << ' ' << r << endl;
//      for (int i = 1; i <= n; i ++) cout << a[i] << " \n"[i == n];
        if (l == r) continue;
        if (l > r || a[r] > a[l]) {
//          cout << a[l] << ' ' << a[r] << endl;
            cout << -1 << endl;
            return;
        }
        deque<int> st;
        for (int i = l + 1; i <= r; i ++) {
            if (a[i] > now) continue;
            if (!st.empty() && a[st.back()] < a[i]) st.pop_back();
            st.push_back(i);
        }
        int lst = l;
        for (auto x: st) {
            swap(a[lst], a[x]);
            lst = x;
            ans.push_back({l, x});
        }
    }
    for (int i = 1; i <= n; i ++) {
        assert(a[i] == b[i]);
    }
    cout << ans.size() << endl;
    for (auto [l, r]: ans) {
        cout << l << ' ' << r << endl;
    }
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int _ = 1;
    cin >> _;
    while (_--){
        solve();
    }
    return 0;
}