#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define maxn 2005
#define put() putchar('\n')
#define Tp template<typename Ty>
#define Ts template<typename Ty,typename... Ar>
using namespace std;
void read(int &x){
    int f=1;x=0;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    x*=f;
}
namespace Debug{
	Tp void _debug(char* f,Ty t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,Ty x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	Tp ostream& operator<<(ostream& os,vector<Ty>& V){os<<"[";for(auto& vv:V) os<<vv<<",";os<<"]";return os;}
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
#define fi first
#define se second
#define mk make_pair
const int mod=1e9+7;
int power(int x,int y=mod-2) {
	int sum=1;
	while (y) {
		if (y&1) sum=sum*x%mod;
		x=x*x%mod;y>>=1;
	}
	return sum;
}
int a[maxn],b[maxn],ans[maxn*maxn][2],cnt,n;
void solve(void) {
	int i,j;cnt=0;
	read(n);
	for (i=1;i<=n;i++) read(a[i]);
	for (i=1;i<=n;i++) read(b[i]);
	for (i=1;i<=n;i++) if (a[i]^b[i]) {
		if (a[i]<b[i]) return puts("-1"),void();
		for (j=i+1;j<=n&&a[i]!=b[i];j++) if (b[i]<=a[j]&&a[j]<=a[i]) {
			++cnt;ans[cnt][0]=i,ans[cnt][1]=j;
			swap(a[i],a[j]);
		}
	}
	for (printf("%d\n",cnt),i=1;i<=cnt;i++) printf("%d %d\n",ans[i][0],ans[i][1]);
}
signed main(void){
//	freopen("1.in","r",stdin);
	int T;
	read(T);while (T--) solve();
	return 0;
}