#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#define rep(a,b) for(int a = 0; a < (b); ++a)
#define pb push_back
#define all(t) t.begin(), t.end()
struct Prz
{
int l,p;
};
const int MAXN = 1e6+5, INF = 2e9+50;
const ull INF_L = (ull)1e19+500;
int n;
int A[2][MAXN];
Prz dp[2][MAXN];
void solve()
{
cin >> n;
rep(j,2) rep(i,n*2) cin >> A[j][i];
dp[0][0] = {1,1}, dp[1][0] = {0,0};
for(int i = 1; i < n*2; ++i)
{
dp[0][i] = {INF,-INF};
if(A[0][i-1] <= A[0][i]) dp[0][i] = {min(dp[0][i].l,dp[0][i-1].l),max(dp[0][i].p,dp[0][i-1].p)};
if(A[1][i-1] <= A[0][i]) dp[0][i] = {min(dp[0][i].l,dp[1][i-1].l),max(dp[0][i].p,dp[1][i-1].p)};
dp[0][i] = {dp[0][i].l+1,dp[0][i].p+1};
dp[1][i] = {INF,-INF};
if(A[0][i-1] <= A[1][i]) dp[1][i] = {min(dp[1][i].l,dp[0][i-1].l),max(dp[1][i].p,dp[0][i-1].p)};
if(A[1][i-1] <= A[1][i]) dp[1][i] = {min(dp[1][i].l,dp[1][i-1].l),max(dp[1][i].p,dp[1][i-1].p)};
}
int x = 2*n-1, y = 0, uz = n;
if(dp[0][2*n-1].l <= n and dp[0][2*n-1].p >= n) y = 0;
else if(dp[1][2*n-1].l <= n and dp[1][2*n-1].p >= n) y = 1;
else
{
cout << "-1" << '\n';
return;
}
string res;
while(x >= 0)
{
if(y == 0) res.pb('A'), --uz;
else res.pb('B');
if(x == 0) break;
if(dp[0][x-1].l <= uz and dp[0][x-1].p >= uz and A[0][x-1] <= A[y][x]) --x, y = 0;
else --x, y = 1;
}
reverse(all(res)), cout << res << '\n';
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int T = 1;
//cin >> T;
while(T--) solve();
return 0;
}
