#include<bits/stdc++.h>
using namespace std;
#define forinc(a,b,c) for(int a=b, __c=c; a<=__c; ++a)
#define fordec(a,b,c) for(int a=b, __c=c; a>=__c; --a)
#define forv(a,b) for(auto &a:b)
#define ii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define all(a) begin(a),end(a)
#define reset(f,x) memset(f,x,sizeof(f))
#define fasty ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
const int N=5e5+5;
int n,a[N][2],dd[N][2];
ii f[N][2];
void dfs(int i,int j){
if(dd[i][j]) return;
dd[i][j]=1;
int mi=1e9, ma=-1e9;
if(a[i][j]<=a[i+1][0]){
dfs(i+1,0);
mi=min(mi,f[i+1][0].fi+1); ma=max(ma, f[i+1][0].se+1);
}
if(a[i][j]<=a[i+1][1]){
dfs(i+1,1);
mi=min(mi,f[i+1][1].fi); ma=max(ma, f[i+1][1].se);
}
f[i][j]={mi,ma};
}
int32_t main(){
fasty;
#define task "build"
if(fopen(task".in","r")) freopen(task".in","r",stdin);
cin>>n; n*=2;
forinc(_,0,1) forinc(i,1,n) cin>>a[i][_];
dd[n][0]=dd[n][1]=1;
dfs(0,0);
if(f[0][0].fi>n/2 || f[0][0].fi>f[0][0].se) return cout<<-1,0;
int pre=0, re=n/2;
forinc(i,1,n){
if(a[i][0]>=a[i-1][pre] && f[i][0].fi<=re-1 && re-1<=f[i][0].se){
pre=0;
re--;
cout<<"A";
}else{
pre=1;
cout<<"B";
}
}
}
