#include <bits/stdc++.h>
#define pii pair<int, int>
#define F first
#define S second
using namespace std;
int N, A[1000006], B[1000006];
const pii emp = pii(0, -1);
pii dp[1000006][2];
pii operator+(pii p, int i)
{
return pii(p.F + i, p.S + i);
}
pii merge(pii p1, pii p2)
{
if (p1.S < p1.F)
return p2;
if (p2.S < p2.F)
return p1;
assert(max(p1.S, p2.S) - min(p1.F, p2.F) + 1 <= p1.S + p2.S - p1.F - p2.F + 2);
return pii(min(p1.F, p2.F), max(p1.S, p2.S));
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
cin >> N;
for (int i = 1; i <= 2 * N; i++)
cin >> A[i];
for (int i = 1; i <= 2 * N; i++)
cin >> B[i];
for (int i = 0; i <= 2 * N; i++)
dp[i][0] = dp[i][1] = emp;
dp[0][0] = pii(0, 0);
for (int i = 1; i <= 2 * N; i++)
{
if (A[i - 1] <= A[i])
dp[i][0] = merge(dp[i][0], dp[i - 1][0] + 1);
if (B[i - 1] <= A[i])
dp[i][0] = merge(dp[i][0], dp[i - 1][1] + 1);
if (A[i - 1] <= B[i])
dp[i][1] = merge(dp[i][1], dp[i - 1][0]);
if (B[i - 1] <= B[i])
dp[i][1] = merge(dp[i][1], dp[i - 1][1]);
}
string ans;
int cur = N, i = 2 * N, j = -1;
if (dp[i][0].F <= cur && cur <= dp[i][0].S)
j = 0;
if (dp[i][1].F <= cur && cur <= dp[i][1].S)
j = 1;
if (j < 0)
{
cout << -1 << '\n';
return 0;
}
while (i)
{
ans.push_back(j == 0 ? 'A' : 'B');
if (j == 0)
{
cur--;
if (A[i - 1] <= A[i] && dp[i - 1][0].F <= cur && cur <= dp[i - 1][0].S)
i--, j = 0;
else
i--, j = 1;
}
else
{
if (A[i - 1] <= B[i] && dp[i - 1][0].F <= cur && cur <= dp[i - 1][0].S)
i--, j = 0;
else
i--, j = 1;
}
}
reverse(ans.begin(), ans.end());
cout << ans << '\n';
}
