#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
ll n, A[1000001], B[1000001];
bool dp[4001][2001][2];
void p(bool zf){
if(zf==0)cout << 'A';
else cout << 'B';
return ;
}
void dfs(ll xf, ll yf, ll zf){
if(xf==0){
p(zf);
return;
}
if(zf==0){
if((A[xf]>=A[xf-1]&&dp[xf-1][yf][0])){
dfs(xf-1, yf, 0);
}
else if((A[xf]>=B[xf-1]&&dp[xf-1][yf][1])){
dfs(xf-1, yf, 1);
}
}
else{
if((B[xf]>=A[xf-1]&&dp[xf-1][yf-1][0])){
dfs(xf-1, yf-1, 0);
}
else if((B[xf]>=B[xf-1]&&dp[xf-1][yf-1][1])){
dfs(xf-1, yf-1, 1);
}
}
p(zf);
return ;
}
int main(){
cin >> n;
for(int i=0; i<2*n; i++){
cin >> A[i];
}
for(int i=0; i<2*n; i++){
cin >> B[i];
}
dp[0][0][0]=1;
dp[0][1][1]=1;
for(int i=1; i<2*n; i++){
for(int t=0; t<=n; t++){
if(t>0){
dp[i][t][1]=((B[i]>=A[i-1]&&dp[i-1][t-1][0])||(B[i]>=B[i-1]&&dp[i-1][t-1][1]));
}
dp[i][t][0]=((A[i]>=A[i-1]&&dp[i-1][t][0])||(A[i]>=B[i-1]&&dp[i-1][t][1]));
}
}
if(dp[2*n-1][n][0]){
dfs(2*n-1, n, 0);
}
else if(dp[2*n-1][n][1]){
dfs(2*n-1, n, 1);
}
else{
cout << -1;
}
return 0;
}
/*
3
2 5 4 9 15 11
6 7 6 8 12 14
*/
