#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <queue>
typedef long long ll;
using namespace std;
const int inf = 1e9 + 5;
void chmin(int& a, const int& b) { a = min(a, b); }
void chmax(int& a, const int& b) { a = max(a, b); }
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
n *= 2;
vector<vector<int> > l(2, vector<int>(n + 2, inf)), r(2, vector<int>(n + 2, -inf));
vector<vector<int> > a(2, vector<int>(n + 2));
a[0][0] = a[1][0] = -inf;
for (int l = 0; l < 2; l++) for (int i = 0; i < n; i++) cin >> a[l][i + 1];
a[0][n + 1] = a[1][n + 1] = inf;
l[0][0] = l[1][0] = r[0][0] = r[1][0] = 0;
for (int i = 1; i <= n + 1; i++)
{
for (int l1 = 0; l1 < 2; l1++) for (int l2 = 0; l2 < 2; l2++) if (a[l1][i - 1] <= a[l2][i] && l[l1][i - 1] != inf)
{
chmin(l[l2][i], l[l1][i - 1]);
chmax(r[l2][i], r[l1][i - 1]);
}
l[1][i]++;
r[1][i]++;
}
int pos = 0, b = n / 2;
string ans;
for (int i = n; i > 0; i--)
{
if (l[0][i] <= b && b <= r[0][i] && a[0][i] <= a[pos][i + 1])
{
ans.push_back('A');
pos = 0;
}
else if (l[1][i] <= b && b <= r[1][i] && a[1][i] <= a[pos][i + 1])
{
ans.push_back('B');
pos = 1;
b--;
}
else
{
cout << "-1\n";
return 0;
}
}
reverse(ans.begin(), ans.end());
cout << ans << "\n";
return 0;
}
