#include "bits/stdc++.h"
using namespace std;
#ifdef duc_debug
#include "bits/debug.h"
#else
#define debug(...)
#endif
const int maxn = 1e6 + 6;
int n, a[maxn][2];
int f[maxn][2][2];
pair<bool, bool> trace[maxn][2][2];
void solve() {
cin >> n;
n = n + n;
for(int j = 0; j < 2; ++j) {
for(int i = 1; i <= n; ++i) {
cin >> a[i][j];
}
}
memset(f, 0x3f, sizeof(f));
for(int i = 0; i < 2; ++i) {
for(int j = 0; j < 2; ++j) {
f[0][i][j] = 0;
}
}
for(int i = 0; i < n; ++i) {
for(int j = 0; j < 2; ++j) {
for(int c = 0; c < 2; ++c) {
for(int nxt = 0; nxt < 2; ++nxt) {
if(a[i + 1][nxt] < a[i][c]) continue;
int cur = f[i][j][c] + (nxt == j ? 1 : -1);
if(cur > 0) {
if(f[i + 1][j][nxt] > cur) {
f[i + 1][j][nxt] = cur;
trace[i + 1][j][nxt] = make_pair(j, c);
}
}
if(cur == 0) {
f[i + 1][0][nxt] = f[i + 1][1][nxt] = 0;
trace[i + 1][0][nxt] = trace[i + 1][1][nxt] = make_pair(j, c);
}
}
}
}
}
int ans = n;
int x = -1, y = -1;
for(int i = 0; i < 2; ++i) {
for(int j = 0; j < 2; ++j) {
if(ans > f[n][i][j]) {
ans = f[n][i][j];
x = i, y = j;
}
}
}
if(ans != 0) {
cout << -1;
return;
}
string res;
for(int i = n; i; --i) {
res += char('A' + y);
pair<bool, bool> cur = trace[i][x][y];
x = cur.first, y = cur.second;
}
reverse(res.begin(), res.end());
cout << res;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
