#include <bits/stdc++.h>
using namespace std;
//macros
typedef long long ll;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define INF 1e9
#define pb push_back
#define fi first
#define se second
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//===================//
// Added libraries //
//===================//
//===================//
//end added libraries//
//===================//
void program();
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
program();
}
//===================//
// begin program //
//===================//
const int MX = 2e6;
int n, a[MX][2];
ii dp[MX][2];
string ans;
void fillAns(int i, int j, int k) {
ans[i] = 'A'+j;
if(i == 0) return;
if(a[i][j] >= a[i-1][0] && dp[i-1][0].fi <= k && k <= dp[i-1][0].se) fillAns(i-1,0,k);
else fillAns(i-1,1,k-1);
}
void program() {
cin>>n;
n *= 2;
RE(i,n) cin>>a[i][0];
RE(i,n) cin>>a[i][1];
dp[0][0] = {0,0};
dp[0][1] = {1,1};
REP(i,1,n) RE(j,2) {
dp[i][j] = {INF,-INF};
RE(k,2) {
if(a[i][j] >= a[i-1][k]) {
dp[i][j].fi = min(dp[i][j].fi, dp[i-1][k].fi+j);
dp[i][j].se = max(dp[i][j].se, dp[i-1][k].se+j);
}
}
}
ans.resize(n);
if(dp[n-1][0].fi <= n/2 && n/2 <= dp[n-1][0].se) fillAns(n-1,0,n/2);
else if(dp[n-1][1].fi <= n/2 && n/2 <= dp[n-1][1].se) fillAns(n-1,1,n/2-1);
else {
cout<<-1<<endl;
return;
}
cout<<ans<<endl;
}
