#include<bits/stdc++.h>
#define sz(x) ((int)x.size())
#define pb push_back
#define ii pair<int,int>
#define iii pair<ii,int>
#define ppb pop_back
#define st first
#define nd second
#define ll long long
#define inf 100000000
#define MOD 998244353
#define LOG 40
#define EPS 0.000000001
#define MAX 1000005
using namespace std;
int n;
pair<int, int> lr[MAX][2];
int c[2][MAX];
void no() {
cout << -1;
exit(0);
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin >> n;
n <<= 1;
for(int i = 0; i < 2; i++)
for(int j = 1; j <= n; j++)
cin >> c[i][j];
lr[0][0] = lr[0][1] = {0, 0};
for(int i = 1; i <= n; i++) {
for(int plan_c = 0; plan_c < 2; plan_c++) { // 0 if a else 1
lr[i][plan_c] = {inf, -inf};
for(int plan_b = 0; plan_b < 2; plan_b++) {
if(c[plan_c][i] >= c[plan_b][i - 1]) {
lr[i][plan_c].st = min(lr[i][plan_c].st, lr[i - 1][plan_b].st + !plan_c);
lr[i][plan_c].nd = max(lr[i][plan_c].nd, lr[i - 1][plan_b].nd + !plan_c);
}
}
}
}
int ind = n;
int req = n / 2;
string ans, _map = "AB";
int last = 2;
while(ind > 0) {
for(int plan_c = 0; plan_c < 2; plan_c++) {
if(lr[ind][plan_c].st <= req and lr[ind][plan_c].nd >= req) {
if(!(last - 2) or c[last][ind + 1] >= c[plan_c][ind]) {
ans.pb(_map[plan_c]);
req -= (!plan_c);
ind--;
last = plan_c;
break ;
}
}
if(plan_c == 1)
no();
}
}
reverse(ans.begin(), ans.end());
cout << ans;
}
