#include<bits/stdc++.h>
#define de fprintf(stderr,"on-%d\n",__LINE__)
//#define int long long
#define fr(i,a,b) for(int i(a),end##i(b);i<=end##i;i++)
#define fd(i,a,b) for(int i(a),end##i(b);i>=end##i;i--)
#define fi first
#define se second
#define pii pair<int,int>
#define mk make_pair
using namespace std;
const int maxn=2500;
int n;
int a[maxn],b[maxn],p[maxn],q[maxn];
pii ans[maxn*maxn];
int top;
void solve(){
	scanf("%d",&n);
	fr(i,1,n){
		scanf("%d",&a[i]);
		p[a[i]]=i;
	}
	fr(i,1,n){
		scanf("%d",&b[i]);
		q[b[i]]=i;
	}
	top=0;
	fr(i,1,n){
		if(p[i]<q[i]||a[q[i]]<i){
			printf("-1\n");
			return ;
		}
		int pre=p[i];
		fd(j,p[i]-1,q[i])if(a[j]>i){
			p[a[j]]=pre;
			a[pre]=a[j];
			ans[++top]=mk(j,pre);
			pre=j;
		}
		a[q[i]]=i;
		p[i]=q[i];
		//fr(j,1,n)printf("%d ",a[j]);printf("\n");
	}
	printf("%d\n",top);
	fr(i,1,top)printf("%d %d\n",ans[i].fi,ans[i].se);
}
signed main(){
#ifdef pig
	freopen("pig.in","r",stdin);
	freopen("pig.out","w",stdout);
#endif
	int t;cin>>t;
	while(t--){
		solve();
	}
	return 0;
}