#include <bits/stdc++.h>
using namespace std;
#define in ({int x=0;int c=getchar(),n=0;for(;!isdigit(c);c=getchar()) n=(c=='-');for(;isdigit(c);c=getchar()) x=x*10+c-'0';n?-x:x;})
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int l,int r){return l+rng()%(r-l+1);}
#define fasty ios_base::sync_with_stdio(0),cin.tie(0);
#define forinc(a,b,c) for(int a=b,_c=c;a<=_c;++a)
#define fordec(a,b,c) for(int a=b,_c=c;a>=_c;--a)
#define forv(a,b) for(auto&a:b)
#define fi first
#define se second
#define pb push_back
#define ii pair<int,int>
#define mt make_tuple
#define all(a) a.begin(),a.end()
#define reset(f, x) memset(f, x, sizeof(f))
#define bit(x,i) ((x>>(i-1))&1)
#define on(x,i) (x|(1ll<<(i-1)))
#define off(x,i) (x&~(1<<(i-1)))
#define gg exit(0);
const int N=1000010;
int n,nn;
int a[N][2];
int f[N][2],mx[N][2],mn[N][2];
main(){
#define task "building4"
//freopen(task".inp","r",stdin);
//freopen(task".out","w",stdout);
n=in; nn=n+n;
forinc(j,0,1) forinc(i,1,nn) a[i][j]=in;
reset(mn,127);
mn[0][0]=mn[0][1]=0, f[0][0]=f[0][1]=1;
forinc(i,0,nn) forinc(j,0,1) forinc(t,0,1) if(f[i][j]){
if(a[i+1][t]>=a[i][j]){
f[i+1][t]=1;
mx[i+1][t]=max(mx[i+1][t],mx[i][j]+t);
mn[i+1][t]=min(mn[i+1][t],mn[i][j]+t);
}
}
forinc(j,0,1){
if(f[nn][j] && mx[nn][j]>=n && n>=mn[nn][j]){
string ans;
int k=n;
fordec(i,nn,1){
ans+=(char)('A'+j); k-=j;
forinc(t,0,1){
if(a[i][j]>=a[i-1][t] && f[i-1][t] && mx[i-1][t]>=k && k>=mn[i-1][t]){
j=t;
break;
}
}
}
reverse(all(ans));
cout<<ans;
gg
}
}
cout<<-1;
}
