#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
const i64 P = 998244353;
void solve() {
    int n;
    cin >> n;
    vector<int> a(n + 1), b(n + 1);
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 1; i <= n; i++) cin >> b[i];
    int ok = 0;
    vector<pair<int, int>> ans;
    while (ok <= n) {
        ok = false;
        int pos = -1, val = -1;
        for (int i = ok + 1; i <= n; i++) {
            if (a[i] != b[i]) {
                pos = i, val = a[i];
                break;
            }
            ok = i;
        }
        if (ok == n) break;
        bool res = true;
        for (int p = pos + 1; p <= n; p++) {
            if (a[p] >= b[pos] && a[p] < val) {
                ans.push_back({pos, p});
                swap(a[pos], a[p]);
                pos = p;
                res = false;
            } 
        }
        if (res) {
            cout << "-1\n";
            return;
        }
    }
    cout << ans.size() << '\n';
    for (auto [x, y] : ans) cout << x << ' ' << y << '\n';
}
int main() {
    ios::sync_with_stdio(0); cin.tie(0), cout.tie(0);
    int t = 1; 
    cin >> t;
    while(t--) solve();
    return 0;
}
/*
10
10 8 2 9 6 5 7 4 3 1
7 1 3 5 9 8 4 10 6 2
*/