#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define MOD 1000000007
typedef long long ll;
typedef pair <int, int> ii;
typedef pair <ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef long double ld;
ll INF=LLONG_MAX;
int const mxn = 1e6+5;
int dp[mxn][2][2]; //pos, cur, min/max = cnt of b;
int a[mxn],b[mxn];
void mins(int &a, int b){
a = min(a,b);
return;
}
void maxs(int &a, int b){
a = max(a,b);
return;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
//freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
int n; cin >> n;
memset(dp,-1,sizeof(dp));
for(int i=1; i<=n*2; i++)cin >> a[i];
for(int i=1; i<=n*2; i++)cin >> b[i];
dp[1][0][0] = dp[1][0][1] = 0;
dp[1][1][0] = dp[1][1][1] = 1;
for(int i=2; i<=n*2; i++){
dp[i][0][0]=dp[i][1][0] = mxn;
dp[i][0][1]=dp[i][1][1] = -1;
if(a[i]>=a[i-1]){
mins(dp[i][0][0],dp[i-1][0][0]);
maxs(dp[i][0][1],dp[i-1][0][1]);
}
if(a[i]>=b[i-1]){
mins(dp[i][0][0],dp[i-1][1][0]);
maxs(dp[i][0][1],dp[i-1][1][1]);
}
if(b[i]>=a[i-1]){
mins(dp[i][1][0],dp[i-1][0][0]+1);
maxs(dp[i][1][1],dp[i-1][0][1]+1);
}
if(b[i]>=b[i-1]){
mins(dp[i][1][0],dp[i-1][1][0]+1);
maxs(dp[i][1][1],dp[i-1][1][1]+1);
}
}
bool cur=0; int cnt=n;
if(dp[n*2][0][0]<=n&&n<=dp[n*2][0][1])cur = 0;
else if(dp[n*2][1][0]<=n&&n<=dp[n*2][1][1])cur = 1;
else{
cout << -1 << endl;
return 0;
}
//start backtracking
string s="";
for(int i=n*2; i>=1; i--){
if(!cur){
s+='A';
if(a[i-1]<=a[i]&&dp[i-1][0][0]<=cnt&&cnt<=dp[i-1][0][1])cur = 0;
if(b[i-1]<=a[i]&&dp[i-1][1][0]<=cnt&&cnt<=dp[i-1][1][1])cur = 1;
}else{
s+='B';
cnt--;
if(a[i-1]<=b[i]&&dp[i-1][0][0]<=cnt&&cnt<=dp[i-1][0][1])cur = 0;
if(b[i-1]<=b[i]&&dp[i-1][1][0]<=cnt&&cnt<=dp[i-1][1][1])cur = 1;
}
}
reverse(all(s));
cout << s << endl;
}
