#include<bits/stdc++.h>
using namespace std;
int main()
{
int N; cin >> N;
vector<int> A(2*N), B(2*N);
for(int i=0; i<2*N; ++i) cin >> A[i];
for(int i=0; i<2*N; ++i) cin >> B[i];
const int INF = 0x3f3f3f3f;
vector<pair<int, int> > dpA(2*N), dpB(2*N); //# of A
dpA[0] = make_pair(1, 1);
dpB[0] = make_pair(0, 0);
for(int i=0; i<2*N-1; ++i)
{
int mina = INF, maxa = -INF, minb = INF, maxb = -INF;
auto [al, ar] = dpA[i]; auto[bl, br] = dpB[i];
if(al != -1)
{
if(A[i] <= A[i+1])
mina = min(mina, al+1), maxa = max(maxa, ar+1);
if(A[i] <= B[i+1])
minb = min(minb, al), maxb = max(maxb, ar);
}
if(bl != -1)
{
if(B[i] <= A[i+1])
mina = min(mina, bl+1), maxa = max(maxa, br+1);
if(B[i] <= B[i+1])
minb = min(minb, bl), maxb = max(maxb, br);
}
if(mina > maxa) mina = maxa = -1;
if(minb > maxb) minb = maxb = -1;
dpA[i+1] = make_pair(mina, maxa);
dpB[i+1] = make_pair(minb, maxb);
}
bool a; int b = 2*N-1, c = N;
if(dpA[2*N-1].first <= N && N <= dpA[2*N-1].second)
a = true;
else if(dpB[2*N-1].first <= N && N <= dpB[2*N-1].second)
a = false;
else
{
puts("-1"); return 0;
}
string s;
if(a) s = "A", c=N-1; else s = "B";
while(b)
{
if(a)
{
if(A[b] >= A[b-1] && dpA[b-1].first != -1 && dpA[b-1].first <= c && c <= dpA[b-1].second)
{
s += "A";
a = true; b = b-1; c = c-1;
}
else
{
s += "B";
a = false; b = b-1; c = c;
}
}
else
{
if(B[b] >= A[b-1] && dpA[b-1].first != -1 && dpA[b-1].first <= c && c <= dpA[b-1].second)
{
s += "A";
a = true; b = b-1; c = c-1;
}
else
{
s += "B";
a = false; b = b-1; c=c;
}
}
}
reverse(s.begin(), s.end());
puts(s.c_str());
}
