#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000005;
int arr[MAXN][2], mna[MAXN][2], mxa[MAXN][2];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int nums; cin >> nums;
for (int j = 0; j <= 1; j++)
for (int i = 1; i <= nums << 1; i++)
cin >> arr[i][j];
for (int i = 1; i <= nums << 1; i++){
for (int j = 0; j <= 1; j++){
int mn = 2 * MAXN, mx = -MAXN;
for (int k = 0; k <= 1; k++)
if (arr[i][j] >= arr[i - 1][k]){
mn = min(mn, mna[i - 1][k]);
mx = max(mx, mxa[i - 1][k]);
}
mn += j; mx += j;
mna[i][j] = mn; mxa[i][j] = mx;
}
}
int req = nums, curr = -1;
vector<int> ans(nums << 1);
for (int i = nums << 1; i >= 1; i--){
for (int j = 0; j <= 1; j++){
if (i != nums << 1 && arr[i][j] > arr[i + 1][curr]) continue;
if (mna[i][j] <= req && mxa[i][j] >= req){
curr = j; break;
}
}
if (curr == -1){
cout << -1; return 0;
}
req -= curr; ans[i - 1] = curr;
}
for (int x : ans) cout << (char)('A' + x);
}
