#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n, a[1000005], b[1000005], c[1000005];
vector<char> ans, res;
void golef(int id)
{
while (true)
{
if (id == 1 || max(a[id-1], b[id-1]) <= c[id]) return;
else
{
if (ans[id-1] != ' ')
{
if (c[id-1] > c[id]) { cout << -1; exit(0); }
return;
}
if (a[id-1] < b[id-1])
{
c[id-1] = a[id-1];
ans[id-1] = 'A';
}
else
{
c[id-1] = b[id-1];
ans[id-1] = 'B';
}
id--;
}
}
}
void gorig(int id)
{
while (true)
{
if (id == n || c[id] <= min(a[id+1], b[id+1])) return;
else
{
if (ans[id+1] != ' ')
{
if (c[id] > c[id+1]) { cout << -1; exit(0); }
return;
}
if (c[id] > max(a[id+1], b[id+1])) { cout << -1; exit(0); }
if (a[id+1] < b[id+1])
{
c[id+1] = b[id+1];
ans[id+1] = 'B';
}
else
{
c[id+1] = a[id+1];
ans[id+1] = 'A';
}
id++;
}
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
n *= 2;
// resize ans/res once (index from 0..n+1, we'll use 1..n)
ans.assign(n + 2, ' ');
res.assign(n + 2, ' ');
for (int i = 1; i <= n; ++i) cin >> a[i];
for (int i = 1; i <= n; ++i) cin >> b[i];
for (int i = 1; i <= n - 1; ++i)
{
if (ans[i] != ' ') continue;
if (min(a[i], b[i]) > max(a[i+1], b[i+1]))
{
cout << -1;
return 0;
}
if (max(a[i], b[i]) > max(a[i+1], b[i+1]))
{
if (a[i] > b[i])
{
c[i] = b[i];
ans[i] = 'B';
}
else
{
c[i] = a[i];
ans[i] = 'A';
}
golef(i);
gorig(i);
}
if (min(a[i], b[i]) > min(a[i+1], b[i+1]))
{
if (a[i+1] > b[i+1])
{
c[i+1] = a[i+1];
ans[i+1] = 'A';
}
else
{
c[i+1] = b[i+1];
ans[i+1] = 'B';
}
golef(i+1);
gorig(i+1);
}
}
int cnt = 0;
for (int i = 1; i <= n; ++i)
{
if (ans[i] == 'A') cnt++;
else if (ans[i] == 'B') cnt--;
else // ans[i] == ' '
{
if (a[i] < b[i])
{
res[i] = 'B';
cnt--;
}
else if (b[i] < a[i])
{
res[i] = 'A';
cnt++;
}
else
{
// nếu bằng nhau, chọn tạm B (giữ tính nhất quán với code cũ)
res[i] = 'B';
cnt--;
}
}
}
for (int i = 1; i <= n; ++i)
{
if (ans[i] == ' ' && res[i] != ' ')
{
int mx = 0, mn = 0, sum = 0, nexi = i;
for (int j = i; j <= n; ++j)
{
if (res[j] == ' ') break;
sum += (res[j] == 'A' ? -2 : 2);
mx = max(mx, sum);
mn = min(mn, sum);
nexi = j;
if (j != n && max(a[j], b[j]) <= min(a[j+1], b[j+1])) break;
}
if (cnt < 0)
{
if (cnt + mx > 0)
{
mx = -cnt;
cnt = 0;
}
else cnt += mx;
int cursum = 0;
bool ok = false;
for (int j = i; j <= nexi; ++j)
{
if (cursum == mx) ok = true;
if (!ok)
{
if (res[j] == 'A') ans[j] = 'B';
else ans[j] = 'A';
}
else ans[j] = res[j];
cursum += (res[j] == 'A' ? -2 : 2);
}
}
else
{
if (cnt + mn < 0)
{
mn = -cnt;
cnt = 0;
}
else cnt += mn;
int cursum = 0;
bool ok = false;
for (int j = i; j <= nexi; ++j)
{
if (cursum == mn) ok = true;
if (!ok)
{
if (res[j] == 'A') ans[j] = 'B';
else ans[j] = 'A';
}
else ans[j] = res[j];
cursum += (res[j] == 'A' ? -2 : 2);
}
}
i = nexi;
}
}
for (int i = 1; i <= n; ++i)
{
if (ans[i] == ' ')
{
if (cnt < 0)
{
cnt += 2;
ans[i] = 'A';
}
else ans[i] = 'B';
}
}
if (cnt != 0) cout << -1;
else
{
for (int i = 1; i <= n; ++i) cout << ans[i];
}
return 0;
}
