#include<bits/stdc++.h>
#define taskname "A"
using namespace std;
int n;
namespace sub1{
const int lim = 2e3 + 5;
bitset<lim>dp[lim][2];
void solve(){
for(int i = 0; i < lim; i++){
dp[i][0].reset();
dp[i][1].reset();
}
vector<int>a(n << 1), b(n << 1);
for(int& x : a){
cin >> x;
}
for(int& x : b){
cin >> x;
}
dp[1][0].set(0);
dp[0][1].set(1);
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
int sum = i + j;
if(sum > 1){
if(i > 0 && ((a[sum - 1] >= a[sum - 2] && dp[i - 1][0].test(j)) || (a[sum - 1] >= b[sum - 2] && dp[i - 1][1].test(j)))){
dp[i][0].set(j);
}
if(j > 0 && ((b[sum - 1] >= a[sum - 2] && dp[i][0].test(j - 1)) || (b[sum - 1] >= b[sum - 2] && dp[i][1].test(j - 1)))){
dp[i][1].set(j);
}
}
}
}
if(!dp[n][0].test(n) && !dp[n][1].test(n)){
return void(cout << -1);
}
vector<int>I(2, n);
int j = int(dp[n][1].test(n));
string ans = "";
for(int _ = (n << 1) - 1; true; _--){
ans += (j == 0 ? 'A' : 'B');
if(_ == 0){
break;
}
I[j]--;
if(!dp[I[0]][j].test(I[1]) || (j == 0 && a[I[0] + I[1]] < a[I[0] + I[1] - 1]) || (j == 1 && b[I[0] + I[1]] < b[I[0] + I[1] - 1])){
j ^= 1;
}
}
reverse(ans.begin(), ans.end());
cout << ans;
}
}
namespace sub2{
const int lim = 5e5 + 5;
pair<int, int>dp[lim][2];
pair<int, int>merge(pair<int, int>a, pair<int, int>b){
return make_pair(min(a.first, b.first), max(a.second, b.second));
}
bool inside(int i, pair<int, int>range){
return range.first <= i && range.second >= i;
}
void solve(){
vector<int>a(n << 1), b(n << 1);
for(int& x : a){
cin >> x;
}
for(int& x : b){
cin >> x;
}
dp[0][0] = make_pair(0, 0);
dp[0][1] = make_pair(1, 1);
for(int i = 1; i < (n << 1); i++){
dp[i][0] = dp[i][1] = make_pair(-1, -1);
if(a[i] >= a[i - 1] && dp[i - 1][0].first != -1){
dp[i][0] = dp[i - 1][0];
}
if(a[i] >= b[i - 1] && dp[i - 1][1].first != -1){
dp[i][0] = (dp[i][0].first == -1 ? dp[i - 1][1] : merge(dp[i][0], dp[i - 1][1]));
}
if(b[i] >= a[i - 1] && dp[i - 1][0].first != -1){
dp[i][1] = make_pair(dp[i - 1][0].first + 1, dp[i - 1][0].second + 1);
}
if(b[i] >= b[i - 1] && dp[i - 1][1].first != -1){
pair<int, int>nxt = make_pair(dp[i - 1][1].first + 1, dp[i - 1][1].second + 1);
dp[i][1] = (dp[i][1].first == -1 ? nxt : merge(dp[i][1], nxt));
}
}
int I = (inside(n, dp[(n << 1) - 1][0]) ? 0 : (inside(n, dp[(n << 1) - 1][1]) ? 1 : -1));
if(I == -1){
return void(cout << -1);
}
string ans = "";
for(int i = (n << 1) - 1; true; i--){
ans += (I == 0 ? 'A' : 'B');
if(i == 0){
break;
}
if(I == 0){
if(a[i] < a[i - 1] || !inside(n, dp[i - 1][0])){
I = 1;
}
}
else if(!inside(--n, dp[i - 1][1]) || b[i] < b[i - 1]){
I = 0;
}
}
reverse(ans.begin(), ans.end());
cout << ans;
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n;
if(n <= 2000){
sub1::solve();
}
else{
sub2::solve();
}
}
