#include <bits/stdc++.h>
#define IO_OP ios::sync_with_stdio(0), cin.tie(0)
#define F first
#define S second
#define V vector
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(), (v).end()
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
const int INF = 1e9 + 7;
signed main()
{
IO_OP;
int n;
cin >> n;
n *= 2;
V<array<int, 2>> a(n);
for(int i = 0; i < n; i++)
cin >> a[i][0];
for(int i = 0; i < n; i++)
cin >> a[i][1];
V<array<int, 2>> l(n, {INF, INF}), r(n, {-INF, -INF});
auto upd = [&] (int i, int j, int L, int R) {
l[i][j] = min(l[i][j], L);
r[i][j] = max(r[i][j], R);
};
upd(0, 0, 0, 0);
upd(0, 1, 1, 1);
for(int i = 1; i < n; i++) {
for(int j = 0; j < 2; j++) if(l[i - 1][j] <= r[i - 1][j]) {
for(int k = 0; k < 2; k++) {
if(a[i - 1][j] <= a[i][k]) {
int L = l[i - 1][j] + k, R = r[i - 1][j] + k;
upd(i, k, L, R);
}
}
}
}
int j = -1;
for(int i = 0; i < 2; i++) {
if(l[n - 1][i] <= n / 2 && n / 2 <= r[n - 1][i])
j = i;
}
if(j == -1) {
cout << -1 << '\n';
return 0;
}
int i = n - 1, need = n / 2;
string s;
while(i >= 0) {
assert(l[i][j] <= need && need <= r[i][j]);
s += 'A' + j;
need -= j;
if(i == 0) break;
for(int k = 0; k < 2; k++) {
if(a[i][j] >= a[i - 1][k] && l[i - 1][k] <= need && need <= r[i - 1][k]) {
j = k;
break;
}
}
i--;
}
reverse(ALL(s));
cout << s << '\n';
}
