#include<bits/stdc++.h>
// #include<atcoder/modint>
// #include<atcoder/convolution>
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define F first
#define S second
#define rs resize
#define ft front()
#define bk back()
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define r0f(i,n) for(int i = n-1; i >= 0; i--)
#define R0F(i,k,n) for(int i = n-1; i >= k; i--)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define SUM(v) (accumulate(all(v), 0LL))
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<endl
#define dout(a) cout<<a<<' '<<#a<<endl
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<endl
#define YN(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
#define yn(x); if(x){cout<<"Yes"<<'\n';}else{cout<<"No"<<'\n';}
#define p2(x) (1LL << (x))
#define pct(x) (__builtin_popcountll((x)))
#define ist(x,y) (((x) >> (y)) & 1)
template<class T, class U> bool ckmin(T& a, const U& b) { return (T)b < a ? a = (T)b, 1 : 0; }
template<class T, class U> bool ckmax(T& a, const U& b) { return a < (T)b ? a = (T)b, 1 : 0; }
const int leg = 1e9 + 7;
const int mod = 998244353;
using namespace std;
// using namespace atcoder;
// using mint = modint998244353;
// using mint = modint1000000007;
const int mxn = 5e5 + 5;
// mint fact[mxn], inv[mxn];
// mint C(int n, int r){return fact[n] * inv[n-r] * inv[r];}
// mint snb(int n, int r){return C(n + r, n);}
void merge(pii &a, pii b){ckmin(a.F, b.F); ckmax(a.S, b.S);}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
//ifstream cin(".in");
//ofstream cout(".out");
// fact[0]=1;FOR(i,1,mxn)fact[i]=fact[i-1]*i;inv[mxn-1]=fact[mxn-1].inv();r0f(i,mxn-1)inv[i]=inv[i+1]*(i+1);
in(n); n*=2; vin(a,n); vin(b,n); vector<vpii>dp(n,vpii(2, {1e9,-1e9})); dp[0][0] = {1,1}; dp[0][1] = {0,0};
FOR(i,1,n){
if(a[i] >= a[i-1])merge(dp[i][0], dp[i-1][0]); if(a[i] >= b[i-1])merge(dp[i][0], dp[i-1][1]);
if(b[i] >= a[i-1])merge(dp[i][1], dp[i-1][0]); if(b[i] >= b[i-1])merge(dp[i][1], dp[i-1][1]);
dp[i][0].F++, dp[i][0].S++;
}
pii cur = {-1,-1}; if(dp[n-1][0].F <= n/2 && dp[n-1][0].S >= n/2)cur = {n-1,0}; if(dp[n-1][1].F <= n/2 && dp[n-1][1].S >= n/2)cur = {n-1,1};
if(cur == mp(-1LL,-1LL)){out(-1); return 0;}
char c = 'A' + cur.S; string ans; ans += c;
int ct = n/2; while(cur.F >= 1){
ct -= (1 - cur.S); int pv = (cur.S == 0 ? a[cur.F] : b[cur.F]); cur.F--;
if(dp[cur.F][0].F <= ct && ct <= dp[cur.F][0].S && a[cur.F] <= pv)cur.S = 0; else cur.S = 1;
ans += (char)('A' + cur.S);
}
reverse(all(ans)); out(ans);
}
