#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tt;
#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())
const int mn = 1e6 + 6;
int a[2][mn], dpLow[2][mn], dpHigh[2][mn];
vector<char> ans;
bool ok (int cur, int i, int need) {
return dpLow[cur][i] <= need && need <= dpHigh[cur][i];
}
void trace (int cur, int i, int need) {
if (i == 1) return ans.push_back(cur + 'A'), void();
for (int pre = 0; pre < 2; pre++) {
if (a[pre][i - 1] <= a[cur][i] && ok(pre, i - 1, need - cur)) {
trace(pre, i - 1, need - cur);
return ans.push_back(cur + 'A'), void();
}
}
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n; cin >> n;
n <<= 1;
for (int j = 0; j < 2; j++)
for (int i = 1; i <= n; i++) cin >> a[j][i];
for (int i = 1; i <= n; i++) {
for (int cur = 0; cur < 2; cur++) {
dpLow[cur][i] = INT_MAX, dpHigh[cur][i] = INT_MIN;
for (int pre = 0; pre < 2; pre++) {
if (a[pre][i - 1] > a[cur][i]) continue;
if (dpLow[pre][i - 1] != INT_MAX)
dpLow[cur][i] = min(dpLow[cur][i], dpLow[pre][i - 1] + cur);
if (dpHigh[pre][i - 1] != INT_MAX)
dpHigh[cur][i] = max(dpHigh[cur][i], dpHigh[pre][i - 1] + cur);
}
}
}
if (!ok(0, n, n / 2) && !ok(1, n, n / 2))
return cout << -1, 0;
if (ok(0, n, n / 2)) trace(0, n, n / 2);
else trace(1, n, n / 2);
for (char c : ans) cout << c;
return 0;
}
