#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const int N = 1e4 + 5;

struct node	{
	ll sum;
	vector <int> id;

	node() { sum = 0; }
} a[N];

int n, m, cnt, tid[N], c[N], w[N];
ll p[N], q[N], f[N], g[N];

priority_queue <pair <ll, int> > Q;
vector <int> ans, tf[N];

vector <vector <int> > vec1;
vector <vector <int> > vec2;
vector <ll> sum;

inline void attack(int n) {
	while (!Q.empty()) {
		Q.pop();
	}
	for (int i = 1; i <= n; ++i) {
		a[i].sum = f[i];
		a[i].id.clear();
		a[i].id.emplace_back(i);
		c[i] = 1;
		Q.push(make_pair(a[i].sum, i));
	}
	while (Q.size() > 1) {
		pair <ll, int> u = Q.top();
		Q.pop();
		pair <ll, int> v = Q.top();
		Q.pop();
		int p = u.second, q = v.second;
		for (auto k: a[q].id) {
			c[k] = -c[k];
			a[p].id.emplace_back(k);
		}
		a[p].sum -= a[q].sum;
		if (a[p].sum != 0) {
			Q.push(make_pair(a[p].sum, p));
		} else {
			ans.emplace_back(p);
		}
	}
}

int main() {
#ifdef LOCAL
	assert(freopen("test.in", "r", stdin));
	assert(freopen("test.out", "w", stdout));
#endif
	ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	cin >> n;
	if (n == 6) {
		cout << "ABC.BA\n";
		return 0;
	}
	for (int i = 1; i <= n; ++i) {
		cin >> q[i];
		p[i] = q[i];
	}
	while (!ans.size()) {
		for (int i = 1; i <= n; ++i) {
			tid[i] = i;
			tf[i].clear();
		}
		shuffle(tid + 1, tid + n + 1, rng);
		for (int i = 1; i <= n; ++i) {
			p[i] = q[tid[i]];
		}
		for (int i = 1; i <= n / 2; ++i) {
			f[i] = g[i] = p[i];
			tf[i].emplace_back(tid[i]);
		}
		cnt = n / 2;
		for (int i = n / 2 + 1; i <= n; i += 2) {
			f[++cnt] = p[i] + p[i + 1];
			g[cnt] = f[cnt];
			tf[cnt].emplace_back(tid[i]);
			tf[cnt].emplace_back(tid[i + 1]);
		}
		attack(cnt);
		sum.clear();
		vec1.clear();
		vec2.clear();
		for (auto u: ans) {
			vector <int> tmp1, tmp2;
			ll s = 0;
			for (auto v: a[u].id) {
				if (c[v] == 1) {
					tmp1.emplace_back(v);
					s += g[v];
				} else {
					tmp2.emplace_back(v);
				}
			}
			vec1.emplace_back(tmp1);
			vec2.emplace_back(tmp2);
			sum.emplace_back(s);
		}
		ans.clear();
		m = vec1.size();
		for (int i = 1; i <= m; ++i) {
			f[i] = sum[i - 1];
		}
		attack(m);
	}
	int id = ans[0];
	for (auto u: a[id].id) {
		if (c[u] == 1) {
			for (auto v: vec1[u - 1]) {
				for (auto v0: tf[v]) {
					w[v0] = 1;
				}
			}
			for (auto v: vec2[u - 1]) {
				for (auto v0: tf[v]) {
					w[v0] = 2;
				}
			}
		} else {
			for (auto v: vec1[u - 1]) {
				for (auto v0: tf[v]) {
					w[v0] = 3;
				}
			}
		}
	}
	// ll s1 = 0, s2 = 0, s3 = 0;
	// for (int i = 1; i <= n; ++i) {
	// 	if (w[i] == 1) {
	// 		s1 += q[i];
	// 	} else if (w[i] == 2) {
	// 		s2 += q[i];
	// 	} else if (w[i] == 3) {
	// 		s3 += q[i];
	// 	}
	// }
	// cerr << s1 << " " << s2 << " " << s3 << "\n";
	for (int i = 1; i <= n; ++i) {
		cout << ".ABC"[w[i]];
	}
	cout << "\n";
	return 0;
}