#include <bits/stdc++.h>
using namespace std;
using ll=long long;
template <typename T> using vec=vector<T>;
template <typename T> inline void ckmax(T& a, const T& b) { if(a<b) { a=b; } }
template <typename T> inline void ckmin(T& a, const T& b) { if(a>b) { a=b; } }
constexpr char nl='\n';
#define fi first
#define se second
#define pb push_back
#define cref const auto&
#define sz(c) (int)(c).size()
#define all(c) c.begin(),c.end()
#define rep(a, b) for(decltype(b) a=0; a<b; ++a)
#ifdef LOCAL
#define DEBUG 1
#else
#define DEBUG 0
#endif
#define ifbug if constexpr(DEBUG)
#define bug(...) ifbug{cerr<<"["#__VA_ARGS__"]: ";bug__(__VA_ARGS__);cerr<<'\n';}
template <typename...A> void bug__(A&&...a){((cerr<<a<<' '),...);}
struct DebugStream {
template <typename T>
constexpr DebugStream& operator<<(T&& value) const {
ifbug std::cerr<<std::forward<T>(value);
return const_cast<DebugStream&>(*this);
}
};
inline constexpr DebugStream cbug{};
constexpr int MAX_N=5e5+6;
constexpr int INF=MAX_N;
constexpr int NEGINF=-MAX_N;
int c[2*MAX_N][2];
int dp_min[2*MAX_N][2];
int dp_max[2*MAX_N][2];
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
int N;
cin>>N;
rep(j, 2) {
for(int i=1; i<=2*N; ++i) {
cin>>c[i][j];
}
}
rep(j, 2) {
dp_min[1][j]=j;
dp_max[1][j]=j;
}
for(int i=2; i<=2*N; ++i) {
rep(j, 2) {
dp_min[i][j]=INF;
dp_max[i][j]=NEGINF;
}
rep(j, 2) {
rep(k, 2) {
if(c[i-1][k] <= c[i][j]) {
ckmin(dp_min[i][j], dp_min[i-1][k]+(j));
ckmax(dp_max[i][j], dp_max[i-1][k]+(j));
}
}
}
}
string wyn; wyn.reserve(2*N);
int j=-1;
rep(jj, 2) {
if(dp_min[2*N][jj] <= N && N <= dp_max[2*N][jj]) {
j=jj;
break;
}
}
if(j==-1) {
cout<<(-1)<<nl;
return 0;
}
int ile=N;
for(int i=2*N; i>=1; --i) {
wyn.pb((j==0 ?'A' :'B'));
ile-=j;
if(i==1) {
break;
}
rep(k, 2) {
if(c[i-1][k] <= c[i][j] && dp_min[i-1][k] <= ile && ile <= dp_max[i-1][k]) {
j=k;
break;
}
}
}
reverse(all(wyn));
cout<<wyn<<nl;
}
