#include <bits/stdc++.h>
using namespace std;
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
  cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
template <class T>
ostream& operator<<(ostream& os, vector<T> V) {
  os << "[ ";
  for (auto v : V) os << v << " ";
  return os << "]";
}
template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> P) {
  return os << "(" << P.first << "," << P.second << ")";
}
template <typename T, typename U>
pair<T, U> operator+(const pair<T, U>& l, const std::pair<T, U>& r) {
  return {l.first + r.first, l.second + r.second};
}
const long long int mod = 1e9 + 7;
const int maxn = 500005;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n;
  cin >> n;
  long long int a[n + 1];
  for (long long int i = 1; i <= n; i++) cin >> a[i];
  string s = "";
  long long int cr = 0;
  for (long long int i = n; i >= 1; i--) {
    for (long long int j = 0; j < a[i]; j++) {
      char c = cr + 'a';
      s += string(i, c);
      cr = (cr + 1) % 26;
    }
    for (long long int j = i - 1; j >= 1; j--) {
      a[j] -= (a[i] * ((i - j + 1)));
    }
    a[i] = 0;
  }
  cout << s << '\n';
}
