#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")


// https://en.wikipedia.org/wiki/Largest_differencing_method
struct Entry {
  Int a[3];
  int u, v, w;
  bool operator<(const Entry &e) const {
    return (a[2] - a[0] < e.a[2] - e.a[0]);
  }
};
int maxBan=0;
string solve(const vector<Int> &A) {
  const int N = A.size();
  for (int ban = 0; ban < N; ++ban) {
    vector<Entry> es(N);
    priority_queue<Entry> que;
    vector<pair<int, string>> stack;
    for (int u = 0; u < N; ++u) {
      Entry &e = es[u];
      e.a[0] = 0;
      e.a[1] = 0;
      e.a[2] = A[u];
      e.u = u;
      e.v = -1;
      e.w = -1;
      que.push(e);
    }
    for (int i = 0; i < ban; ++i) que.pop();
    for (; ; ) {
      if (que.size() <= 1) goto failed;
      const Entry e = que.top(); que.pop();
      const Entry f = que.top(); que.pop();
      const int u = es.size(); es.emplace_back();
      Entry &g = es[u];
      for (int k = 0; k < 3; ++k) g.a[k] = e.a[k] + f.a[2 - k];
      sort(g.a, g.a + 3);
      g.u = u;
      g.v = e.u;
      g.w = f.u;
      if (g.a[0] == g.a[2]) {
        stack.emplace_back(u, "ABC");
        break;
      }
      que.push(g);
    }
    {
      string ans(N, '.');
      for (; stack.size(); ) {
        const int u = stack.back().first;
        const string s = stack.back().second;
        stack.pop_back();
        const Entry &g = es[u];
        if (~g.v) {
          const Entry &e = es[g.v];
          const Entry &f = es[g.w];
          bool used[3] = {};
          string se(3, '.'), sf(3, '.');
          for (int k = 0; k < 3; ++k) {
            for (int l = 0; l < 3; ++l) if (!used[l] && g.a[l] == e.a[k] + f.a[2 - k]) {
              used[l] = 1;
              se[k] = sf[2 - k] = s[l];
              break;
            }
          }
          for (int l = 0; l < 3; ++l) assert(used[l]);
          stack.emplace_back(e.u, se);
          stack.emplace_back(f.u, sf);
        } else {
          ans[u] = s[2];
        }
      }
chmax(maxBan,ban);
      return ans;
    }
   failed:{}
  }
  return "";
}

void test() {
  constexpr int N = 10'000;
  constexpr int T = 1000;
  int failure = 0;
  for (int seed = 0; seed < T; ++seed) {
    mt19937_64 rng(seed);
    vector<Int> A(N);
    for (int i = 0; i < N; ++i) A[i] = 1 + rng() % 1'000'000'000'000LL;
    const string ans = solve(A);
    if (ans.size()) {
      assert(ans != string(N, '.'));
      Int sums[3] = {};
      for (int i = 0; i < N; ++i) if (ans[i] != '.') sums[ans[i] - 'A'] += A[i];
      for (int k = 0; k < 3; ++k) assert(sums[0] == sums[k]);
    } else {
      ++failure;
    }
  }
  cerr << "fail " << failure << " / " << T << endl;
cerr<<"maxBan="<<maxBan<<endl;
}

int main() {
#ifdef LOCAL
  test();
#endif
  
  int N;
  for (; ~scanf("%d", &N); ) {
    vector<Int> A(N);
    for (int i = 0; i < N; ++i) {
      scanf("%lld", &A[i]);
    }
    
    const string ans = solve(A);
    puts(ans.c_str());
  }
  return 0;
}