#include <bits/stdc++.h>

#define eb emplace_back
#define ep emplace
#define fi first
#define se second
#define in read<int>()
#define lin read<ll>()
#define rep(i, x, y) for(int i = (x); i <= (y); i++)
#define per(i, x, y) for(int i = (x); i >= (y); i--)

using namespace std;

using ll = long long;
using db = double;
using pii = pair < int, int >;
using vec = vector < int >;
using veg = vector < pii >;

template < typename T > T read() {
	T x = 0; bool f = 0; char ch = getchar();
	while(!isdigit(ch)) f |= ch == '-', ch = getchar();
	while(isdigit(ch)) x = x * 10 + (ch ^ 48), ch = getchar();
	return f ? -x : x;
}

template < typename T > void chkmax(T &x, const T &y) { x = x > y ? x : y; }
template < typename T > void chkmin(T &x, const T &y) { x = x < y ? x : y; }

const int N = 1e6 + 10;

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

int get(int *a, int x) {
	rep(i, 1, n) if(a[i] == x) return i;
	return -1;
}

void solve() {
	n = in; rep(i, 1, n) a[i] = in; rep(i, 1, n) b[i] = in;
	veg ans;
	rep(i, 1, n) {
		int ta = get(a, i), tb = get(b, i);
		if(ta < tb) return puts("-1"), void();
		vec pot;
		rep(j, tb, ta - 1) {
			if(a[j] > i) {
				if(!pot.size() || a[j] < a[pot.back()]) pot.eb(j);
			}
		}
		reverse(pot.begin(), pot.end());
		for(auto v : pot) swap(a[ta], a[v]), ans.eb(ta, v), ta = v;
		assert(a[tb] == i);
	}
	printf("%lu\n", ans.size());
	for(auto v : ans) printf("%d %d\n", v.fi, v.se);
}

int main() {
#ifdef YJR_2333_TEST
	freopen("1.in", "r", stdin);
#endif
	for(int T = in; T; T--) solve();
	return 0;
}