#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using db = double;
using pii = pair<int, int>;
int n;
int a[2006];
int main() {
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  string s;
  int t = 0;
  for (int i = n; i >= 1; --i)
    while (a[i]) {
      for (int j = i; j >= 1; --j) a[j] -= i + 1 - j;
      for (int j = 0; j < i; ++j) s.push_back('a' + t);
      t ^= 1;
    }
  cout << s << endl;
  return 0;
}
