#include <iostream>
using namespace std;
const int N = 1<<20;
int a[N][2], Poss[N][2];
pair<int,int> Rng[N][2];
int main(){
int n;
cin>>n;
n += n;
for (int i=1;i<=n;i++)
cin>>a[i][0];
for (int i=1;i<=n;i++)
cin>>a[i][1];
Poss[0][0] = 1;
Rng[0][0] = {0, 0};
for (int i=1;i<=n;i++){
for (int k : {0, 1}){
for (int j : {0, 1}){
if (Poss[i-1][j] == 0 or a[i-1][j] > a[i][k])
continue;
auto [l, r] = Rng[i][k];
auto [L, R] = Rng[i-1][j];
if (Poss[i][k] == 0)
Rng[i][k] = {L + !k, R + !k};
else
Rng[i][k] = {min(L, l) + !k, max(R, r) + !k};
Poss[i][k] = 1;
}
}
}
int I = n, J = 0, countA = n / 2;
if (!Poss[I][J] or Rng[I][J].first > countA or Rng[I][J].second < countA)
J = 1;
if (!Poss[I][J] or Rng[I][J].first > countA or Rng[I][J].second < countA)
return cout<<"-1\n", 0;
string s;
while (I != 0){
s += char('A' + J);
countA -= !J;
for (int k : {0, 1}){
if (Poss[I-1][k] and a[I-1][k] < a[I][J] and Rng[I-1][k].first <= countA and Rng[I-1][k].second >= countA){
J = k, I--;
break;
}
}
}
for (int i=n-1;i>=0;i--)
cout<<s[i];
cout<<'\n';
}
