// FUCKED UP FUCKED UP FUCKED UP FUCKED UP FUCKED UP
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O2,no-stack-protector,unroll-loops,fast-math")
#define F first
#define S second
#define pb push_back
#define SZ(x) (ll)(x.size())
#define all(x) x.begin(),x.end()
#define MP make_pair
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll maxn=1e6+10, maxm=1e6+10, lg=10, mod=1e9+7, inf=1e18;
ll n,a[maxn][2],mn[maxn][2],mx[maxn][2];
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
for(int i=0;i<maxn;i++) mn[i][0]=mn[i][1]=inf, mx[i][0]=mx[i][1]=-inf;
cin>>n; n*=2;
for(int b:{0,1})for(int i=1;i<=n;i++) cin>>a[i][b];
mn[1][0]=mx[1][0]=0;
mn[1][1]=mx[1][1]=1;
for(int i=2;i<=n;i++)for(ll b:{0,1})for(int bb:{0,1})if(a[i][b]>=a[i-1][bb]){
mn[i][b]=min(mn[i][b],mn[i-1][bb]+b);
mx[i][b]=max(mx[i][b],mx[i-1][bb]+b);
}
ll bb=n/2,gg=inf;
string ans="";
for(int i=n;i>=1;i--){
bool F=0;
for(int b:{0,1}){
if(a[i][b]<=gg && mn[i][b]<=bb && bb<=mx[i][b]){
bb-=b;
ans=(b ? 'B':'A')+ans;
gg=a[i][b];
F=1;
break;
}
}
if(!F) return cout<<-1,0;
}
cout<<ans;
return 0;
}
// a denial a denial a denial a denial a denial a denial
