#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define all(aaa) aaa.begin(), aaa.end()
const int N = 1e6 + 5;
pair<int, int> dp[N][2];
int a[N][2];
int n;
pair<int, int> mrg(pair<int, int> a, pair<int, int> b) {
if (a.first > a.second)
return b;
if (b.first > b.second)
return a;
return {min(a.first, b.first), max(a.second, b.second)};
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
for (int j = 0; j < 2; j++) {
for (int i = 0; i < n + n; i++) {
cin >> a[i][j];
}
}
for (int i = 0; i <= n + n; i++) {
for (int j = 0; j < 2; j++) {
dp[i][j] = {1, 0};
}
}
dp[1][0] = {0, 0};
dp[1][1] = {1, 1};
for (int i = 1; i < n + n; i++) {
for (int j = 0; j < 2; j++) {
for (int k = 0; k < 2; k++) {
if (a[i - 1][j] <= a[i][k]) {
dp[i + 1][k] = mrg(dp[i + 1][k], dp[i][j]);
}
}
}
dp[i + 1][1].first++;
dp[i + 1][1].second++;
}
int x = n + n, y = -1, z = n;
for (int i = 0; i < 2; i++) {
if (dp[n + n][i].first <= n && n <= dp[n + n][i].second) {
y = i;
break;
}
}
if (y == -1) {
cout << "-1";
}
else {
string ans;
while (true) {
ans.push_back({y ? 'B' : 'A'});
if (x == 1)
break;
z -= y;
x--;
for (int i = 0; i < 2; i++) {
if (a[x - 1][i] <= a[x][y] &&
dp[x][i].first <= z && z <= dp[x][i].second) {
y = i;
break;
}
}
}
reverse(all(ans));
cout << ans << "\n";
}
}
