#include <bits/stdc++.h>
using namespace std;
const int N=1e6+10;
int a[N], b[N], n;
pair<int, int> f[N][2];
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i=1; i<=n*2; ++i) cin >> a[i];
for (int i=1; i<=n*2; ++i) cin >> b[i];
f[1][0]={1, 1};
f[1][1]={0, 0};
for (int i=2; i<=n*2; ++i){
f[i][0]={-1, -1};
f[i][1]={-1, -1};
if (a[i-1]<=a[i] && f[i-1][0].first!=-1){
f[i][0]={f[i-1][0].first+1, f[i-1][0].second+1};
}
if (b[i-1]<=a[i] && f[i-1][1].first!=-1){
if (f[i][0].first==-1) f[i][0]={f[i-1][1].first+1, f[i-1][1].second+1};
else{
assert(max(f[i-1][0].first, f[i-1][1].first)<=min(f[i-1][0].second, f[i-1][1].second)+1);
f[i][0]={min(f[i][0].first, f[i-1][1].first+1), max(f[i][0].second, f[i-1][1].second+1)};
}
}
if (b[i-1]<=b[i] && f[i-1][1].first!=-1){
f[i][1]={f[i-1][1].first, f[i-1][1].second};
}
if (a[i-1]<=b[i] && f[i-1][0].first!=-1){
if (f[i][1].first==-1) f[i][1]={f[i-1][0].first, f[i-1][0].second};
else{
assert(max(f[i-1][0].first, f[i-1][1].first)<=min(f[i-1][0].second, f[i-1][1].second)+1);
f[i][1]={min(f[i][1].first, f[i-1][0].first), max(f[i][1].second, f[i-1][0].second)};
}
}
}
string ans;
auto trace=[&](auto &&self, int i, int j, int sum) -> void {
if (j==0){
--sum;
ans.push_back('A');
if (i==1) return;
if (a[i-1]<=a[i] && f[i-1][0].first<=sum && sum<=f[i-1][0].second && sum){
self(self, i-1, 0, sum);
}else{
self(self, i-1, 1, sum);
}
}else{
ans.push_back('B');
if (i==1) return;
if (b[i-1]<=b[i] && f[i-1][1].first<=sum && sum<=f[i-1][1].second){
self(self, i-1, 1, sum);
}else{
self(self, i-1, 0, sum);
}
}
};
if (f[n*2][0].first<=n && n<=f[n*2][0].second){
trace(trace, n*2, 0, n);
reverse(ans.begin(), ans.end());
cout << ans << '\n';
}else if (f[n*2][1].first<=n && n<=f[n*2][1].second){
trace(trace, n*2, 1, n);
reverse(ans.begin(), ans.end());
cout << ans << '\n';
}else{
cout << -1 << '\n';
}
return 0;
}
