#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ar array
const int mxN=5e5;
int n, a[2*mxN][2], dp[2*mxN][2][2]; // take a, b, max a, max b
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for (int j : {0, 1})
for (int i=0; i<2*n; ++i)
cin >> a[i][j];
memset(dp, -1, sizeof(dp));
dp[0][0][0]=1, dp[0][0][1]=0, dp[0][1][1]=1, dp[0][1][0]=0;
for (int i=1; i<2*n; ++i) {
for (int j : {0, 1}) {
for (int k : {0, 1}) {
if (a[i-1][k]<=a[i][j]&&dp[i-1][k][0]!=-1) {
dp[i][j][0]=max(dp[i][j][0], dp[i-1][k][0]+(j==0));
dp[i][j][1]=max(dp[i][j][1], dp[i-1][k][1]+(j==1));
}
}
}
}
for (int x : {0, 1}) {
if (dp[2*n-1][x][0]>=n&&dp[2*n-1][x][1]>=n) {
string ans(2*n, 'A');
int need[2]={n, n};
for (int i=2*n-1, j=x; ~i; --i) {
ans[i]='A'+j;
--need[j];
if (i) {
bool ok=0;
for (int k : {0, 1})
if (a[i-1][k]<=a[i][j]&&dp[i-1][k][0]>=need[0]&&dp[i-1][k][1]>=need[1]) {
j=k;
ok=1;
break;
}
assert(ok);
}
}
cout << ans;
return 0;
}
}
cout << -1;
return 0;
}
