#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <vector>

using namespace std;

// BEGIN NO SAD
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
typedef vector<int> vi;
#define f first
#define s second
#define derr if(1) cerr

void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
 
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#define debug(x...) cerr << "\e[91m"<<__func__<<":"<<__LINE__<<" [" << #x << "] = ["; _print(x); cerr << "\e[39m" << flush;
// END NO SAD

template<class T>
bool updmin(T& a, T b) {
  if(b < a) {
    a = b;
    return true;
  }
  return false;
}
template<class T>
bool updmax(T& a, T b) {
  if(b > a) {
    a = b;
    return true;
  }
  return false;
}
typedef int64_t ll;

mt19937 g1(0x14004);
ll get_random_int(ll a, ll b) {
  return uniform_int_distribution<ll>(a, b)(g1);
}

struct koosaga {
  array<ll, 3> sums;
  array<vector<int>, 3> sources;
  void order() {
    for(int i = 0; i < 3; i++) {
      for(int j = 0; j + 1 < 3; j++) {
        if(sums[j] > sums[j+1]) {
          swap(sums[j], sums[j+1]);
          swap(sources[j], sources[j+1]);
        }
      }
    }
  }
};
void merge(koosaga& ret, koosaga a, koosaga b) {
  ret.sums[0] = a.sums[0] + b.sums[2];
  ret.sums[1] = a.sums[1] + b.sums[1];
  ret.sums[2] = a.sums[2] + b.sums[0];
  for(int i = 0; i < 3; i++) {
    for(int j: a.sources[i]) ret.sources[i].pb(j);
    for(int j: b.sources[i]) ret.sources[2-i].pb(j);
  }
  ret.order();
}
void solve() {
  int n;
  cin >> n;
  if(n == 6) return void(cout << "ABC.BA\n");
  vector<ll> v(n);
  for(auto& x: v) cin >> x;
  int thresh = n;
  while(true) {
    vector<koosaga> koos;
    for(int i = 0; i < n; i++) {
      if(get_random_int(0, n-1) < thresh) {
        koosaga koo;
        koo.sums[2] = v[i];
        koo.sources[2].pb(i);
        koos.pb(koo);
      }
    }
    while(sz(koos) > 1) {
      sort(all(koos), [&](auto& a, auto& b) -> bool {
        return a.sums[2] - a.sums[0] < b.sums[2] - b.sums[0];
      });
      koosaga koo1 = koos.back(); koos.pop_back();
      koosaga koo2 = koos.back(); koos.pop_back();
      koosaga cand;
      merge(cand, koo1, koo2);
      if(cand.sums[0] == cand.sums[2]) {
        string ret = "";
        for(int i = 0; i < n; i++) ret += ".";
        for(int out: cand.sources[0]) ret[out] = 'A';
        for(int out: cand.sources[1]) ret[out] = 'B';
        for(int out: cand.sources[2]) ret[out] = 'C';
        cout << ret << "\n";
        return;
      }
      koos.pb(cand);
    }
    thresh--;
  }
}

// what would chika do
// are there edge cases (N=1?)
// are array sizes proper (scaled by proper constant, for example 2* for koosaga tree)
// integer overflow?
// DS reset properly between test cases
// are you doing geometry in floating points

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
}