#include<bits/stdc++.h>
using namespace std;
bool M1;
#define PI 3.14159265358979323846
#define sz(a) (int)a.size()
#define all(x) x.begin(),x.end()
#define ii pair<int,int>
#define iii pair<int,ii>
#define iv pair<ii,ii>
#define se second
#define fi first
#define ffi fi.fi
#define sfi se.fi
#define sse se.se
#define fse fi.se
#define lt(i, c, d) for(int i = c; i <= d; ++i)
#define fl(i, c, d) for(int i = d; i >= c; --i)
#define pb push_back
#define emb emplace_back
#define emf emplace_front
#define em emplace
#define look_memory cerr<<abs(&M2-&M1)/1024.0/1024<<'\n'
#define look_time cerr << "TIME : " << clock() * 0.001 << "s" <<'\n'
const int N=1e6+5,lg=30,mod=1e9+7,inf=1e9;
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
int Rand(int u,int v){
return u+rd()%(v-u+1);
}
int dx[]={1,0,-1,0,1,1,-1,-1};
int dy[]={0,-1,0,1,1,-1,1,-1};
int node,a[2][N];
ii dp[N][2];
bool M2;
void solve(){
cin >> node ;
for(int j=0;j<=1;++j)
for(int i=1;i<=node*2;++i)cin >> a[j][i];
for(int i=1;i<=node*2;++i){
for(int j=0;j<=1;++j){
dp[i][j]={inf,-inf};
for(int k=0;k<=1;++k){
if(a[j][i]<a[k][i-1])continue;
dp[i][j].fi=min(dp[i][j].fi,dp[i-1][k].fi+(1-j));
dp[i][j].se=max(dp[i][j].se,dp[i-1][k].se+(1-j));
}
}
}
int ok=-1;
vector<int>res;
for(int i=1;i<=node*2;++i)cerr <<dp[i][0].fi<<" "<<dp[i][0].se<<" "<<dp[i][1].fi<<" "<<dp[i][1].se<<'\n';
for(int i=0;i<=1;++i){
if(dp[node*2][i].fi<=node&&node<=dp[node*2][i].se){
ok=i;
}
}
// cout <<ok<<" "<<node<<'\n';
if(ok==-1){
cout <<-1;return;
}
int cnt=node;
for(int i=node*2;i>=1;--i){
res.emb(ok);
cnt-=(1-ok);
int val=a[ok][i];
if(val>=a[0][i-1]&&dp[i-1][0].fi<=cnt&&cnt<=dp[i-1][0].se)ok=0;
else ok=1;
}
reverse(all(res));
for(auto x:res)cout <<(!x?'A':'B');
}
main()
{
srand(time(0));
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
#define task "aws"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
int t=1;
// cin >> t;
while(t--){
solve();
}
look_memory;
look_time;
}
