#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 500001*2;
const int inf = 2e9;
int n;
int a[maxn][2];
int dpLow[maxn][2], dpHigh[maxn][2]; //range of # of B's
void setMin(int &x, int y) {
x = min(x, y);
}
void setMax(int &x, int y) {
x = max(x, y);
}
bool solve(int i, int b, int hi) {
if (i==-1) {
return true;
}
if (a[i][0]<=hi && dpLow[i][0]<=b && b<=dpHigh[i][0]) {
solve(i-1,b,a[i][0]);
cout<<"A";
return true;
}
if (a[i][1]<=hi && b>0 && dpLow[i][1]<=b && b<=dpHigh[i][1]) {
solve(i-1,b-1,a[i][1]);
cout<<"B";
return true;
}
return false;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n;
n *= 2;
for (int j=0; j<2; j++) {
for (int i=0; i<n; i++) {
cin>>a[i][j];
}
}
for (int i=0; i<n; i++) {
for (int j=0; j<2; j++) {
dpLow[i][j] = inf;
dpHigh[i][j] = -inf;
}
}
dpLow[0][0] = dpHigh[0][0] = 0;
dpLow[0][1] = dpHigh[0][1] = 1;
for (int i=0; i<n-1; i++) {
for (int j=0; j<2; j++) {
if (a[i][j] <= a[i+1][0]) {
setMin(dpLow[i+1][0], dpLow[i][j]);
setMax(dpHigh[i+1][0], dpHigh[i][j]);
}
if (a[i][j] <= a[i+1][1]) {
setMin(dpLow[i+1][1], dpLow[i][j]+1);
setMax(dpHigh[i+1][1], dpHigh[i][j]+1);
}
}
}
if (!solve(n-1,n/2,inf)) {
out(-1);
}
return 0;
}
