#include <bits/stdc++.h>
using namespace std;
int n, d[2001];
string s;
char ch = 'a';
int main() {
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> d[i];
  for (int i = n; i > 0; i--) {
    while (d[i] > 0) {
      if (ch == 'e') ch = 'a';
      for (int j = i; j > 0; j--) d[j] -= i + 1 - j;
      for (int j = 0; j < i; j++) cout << ch;
      ch++;
    }
  }
  cout << s << endl;
  return 0;
}
