#include <bits/stdc++.h>
using namespace std;
int w[2005], n, x;
char c;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> w[i];
  c = 'a';
  for (int i = 2000; i > 0; i--)
    while (w[i]) {
      for (int j = 1; j <= i; j++) {
        cout << c;
        w[j] -= i - j + 1;
      }
      if (c == 'z')
        c = 'a';
      else
        c++;
    }
  return 0;
}
