#ifndef _DEBUG
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin(), (x).end()
template <class T>
istream &operator>>(istream &in, vector<T> &a)
{
for (T &x : a)
in >> x;
return in;
}
template <class T>
ostream &operator<<(ostream &out, const vector<T> &a)
{
for (T x : a)
out << x << " ";
out << "\n";
return out;
}
struct Range
{
int low, high;
Range operator+(Range other)
{
if (low < 0)
return other;
if (other.low < 0)
return *this;
assert(max(low, other.low) <= min(high, other.high) + 1);
return {min(low, other.low), max(high, other.high)};
}
Range operator+(int x)
{
return {low + x, high + x};
}
};
signed main()
{
cin.tie(0);
ios_base::sync_with_stdio(false);
int n;
cin >> n;
vector<int> a(2 * n);
vector<int> b(2 * n);
cin >> a >> b;
vector<Range> rA(2 * n, {-1000000000, -1000000000}), rB(2 * n, {-1000000000, -1000000000});
rA[0] = {0, 0};
rB[0] = {1, 1};
for (int i = 1; i < n * 2; i++)
{
if (a[i] >= a[i - 1])
rA[i] = rA[i] + rA[i - 1];
if (a[i] >= b[i - 1])
rA[i] = rA[i] + rB[i - 1];
if (b[i] >= a[i - 1])
rB[i] = (rB[i] + rA[i - 1]);
if (b[i] >= b[i - 1])
rB[i] = (rB[i] + rB[i - 1]);
rB[i] = rB[i] + 1;
}
string out;
int needed = n;
int last_taken = 10000000000000;
while (rA.size())
{
if (needed >= rA.back().low && needed <= rA.back().high && a.back() <= last_taken)
{
out.push_back('A');
last_taken = a.back();
}
else if (needed >= rB.back().low && needed <= rB.back().high && b.back() <= last_taken)
{
out.push_back('B');
last_taken = b.back();
needed--;
}
else
{
cout << -1;
return 0;
}
rA.pop_back();
rB.pop_back();
a.pop_back();
b.pop_back();
}
reverse(out.begin(), out.end());
cout << out;
}
