#include <bits/stdc++.h>
using namespace std;
#define dbgv(v) cout<<#v<<" = "; f(i,0,v.size()) cout<<v[i]<<" "; cout<<endl
#define dbga(a,x,y) cout<<#a<<" = "; f(i,x,y) cout<<a[i]<<" "; cout<<endl
#define erorp(x) cout<<#x<<"={"<<(x.F)<<" , "<<x.S<<"}"<<endl
#define eror(x) cout<<#x<<'='<<(x)<<endl
#define f_(i,a,b) for(int i=a;i>=b;i--)
#define f(i,a,b) for(int i=a;i<b;i++)
#define nb(x) __builtin_popcount(x)
#define all(v) v.begin(),v.end()
#define bit(n,k) (((n)>>(k))&1)
#define Add(x,y) x=(x+y)%mod
#define maxm(a,b) a=max(a,b)
#define minm(a,b) a=min(a,b)
#define lst(x) x[x.size()-1]
#define sz(x) int(x.size())
#define mp make_pair
#define ll long long
#define pb push_back
#define S second
#define F first
const int N=1e6+99,S=2,inf=1e9+9;
int n,t,a[N][S],L[N][2],R[N][2],seg[N<<2][S];
string ans;
void solve(int id,int x,int nxt){
if(id==0) return ;
f(i,0,S){
if(a[id][i]<=nxt && L[id][i]<=x && x<=R[id][i]){
ans+=char('A'+i);
solve(id-1,x-i,a[id][i]);
return ;
}
}
assert(0);
}
int main(){
cin>>n; n<<=1;
f(i,1,n+1) cin>>a[i][0];
f(i,1,n+1) cin>>a[i][1];
L[1][0]=R[1][0]=0;
L[1][1]=R[1][1]=1;
f(i,2,n+1){
L[i][0]=L[i][1]=N;
R[i][0]=R[i][1]=-N;
f(p,0,S){
f(k,0,S){
if(a[i-1][p]>a[i][k]) continue ;
minm(L[i][k],L[i-1][p]+k);
maxm(R[i][k],R[i-1][p]+k);
}
}
}
f(i,0,S){
if(L[n][i]<=n/2 && n/2<=R[n][i]) break;
if(i==1){
return cout<<-1,0;
}
}
solve(n,n/2,inf);
reverse(all(ans));
cout<<ans;
}
