#include <bits/stdc++.h>
#define pb push_back
#define all(x) begin(x), end(x)
using namespace std;
#define N 2000050
int n, v[2][N];
char t[2]={'A','B'};
int dpmin[N][2], dpmax[N][2];
int solve_min(int i, int flag){
if(i == 0) return 0;
if(dpmin[i][flag] != -1) return dpmin[i][flag];
int ans=(int)(1e8);
for(int c=0;c<2;c++)
if(v[c][i] <= v[flag][i+1]) ans = min(ans, solve_min(i-1, c) + c);
return dpmin[i][flag]=ans;
}
int solve_max(int i, int flag){
if(i == 0) return 0;
if(dpmax[i][flag] != -1) return dpmax[i][flag];
int ans=-(int)(1e8);
for(int c=0;c<2;c++)
if(v[c][i] <= v[flag][i+1]) ans = max(ans, solve_max(i-1, c) + c);
return dpmax[i][flag]=ans;
}
int main(){
ios::sync_with_stdio(false); cin.tie(0);
cin>>n;
// if(n>3000)return 0;
n *= 2;
for(int i = 1; i <= n; i++) cin>>v[0][i];
for(int i = 1; i <= n; i++) cin>>v[1][i];
v[0][n+1] = v[1][n+1]=(int)(1e9);
memset(dpmin,-1,sizeof dpmin);
memset(dpmax,-1,sizeof dpmax);
string s;
int qb=n/2,ant=0, qa=n/2;
// cout<<solve_min(n, 0)<<" "<<solve_max(n, 0)<<"\n";
for(int i=n;i>=1;i--){
if(solve_min(i, ant) <= qb and qb <= solve_max(i, ant)){
//testa colocar A
int mn1 = solve_min(i - 1, 0), mx1 = solve_max(i-1, 0);
int mn2 = solve_min(i - 1, 1), mx2 = solve_max(i-1, 1);
if(mn1 <= qb and qb <= mx1 and qa and v[0][i] <= v[ant][i+1]) s.pb('A'),ant=0, qa--;
else s.pb('B'), qb--,ant=1;
}
else cout<<"-1\n", exit(0);
}
reverse(all(s));
if(qb != 0 or qa != 0) cout<<"-1\n";
else cout<<s<<"\n";
}
