#include<bits/stdc++.h>
using namespace std;
#define int long long
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define INF (int)1e17
#define MX (int)3e5+5
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
in merge(in x1, in x2)
{
if(x1 == (in){-1, 0})
return x2;
else if(x2 == (in){-1, 0})
return x1;
else if(x1 == (in){0,0})
return x2;
else if(x2 == (in){0,0})
return x1;
else
return {min(x1[0], x2[0]), max(x1[0], x2[0])};
}
in sp(in x, int u)
{
if(u == 0)
return x;
if(x == (in){-1, 0})
return x;
else
return {x[0]+1, x[1]+1};
}
bool belongs(int p, in x)
{
return ((x[0] <= p) && (p <= x[1]));
}
signed main()
{
fast();
int n; cin >> n; n = 2*n;
vector<in> x(n+1);
for(int i = 1; i <= n; i++)
cin >> x[i][0];
for(int i = 1; i <= n; i++)
cin >> x[i][1];
in dp[n+1][2];
dp[0][0] = {0,0};
dp[0][1] = {0,0};
x[0] = {0,0};
for(int i = 1; i <= n; i++)
{
for(int j = 0; j < 2; j++)
{
dp[i][j] = {0,0};
for(int k = 0; k < 2; k++)
{
if(x[i-1][k] <= x[i][j])
dp[i][j] = merge(dp[i][j], sp(dp[i-1][k], j));
}
}
}
if(belongs(n/2, dp[n][0]) || belongs(n/2, dp[n][1]))
{
int g = n/2;
vector<char> c(n+1);
int j = 0;
if(belongs(g, dp[n][1]))
j = 1;
for(int i = n; i >= 1; i--)
{
c[i] = 'A'+j;
g-=j;
for(int k = 0; k < 2; k++)
{
if(x[i-1][k] <= x[i][j])
{
if(belongs(g, dp[i-1][k]))
{
j = k;
break;
}
}
}
}
for(int i = 1; i <= n; i++)
cout << c[i];
cout << "\n";
}
else
cout << "-1\n";
return 0;
}
