#include <bits/stdc++.h>
using namespace std;
long long int n, a, unutma, j;
long long int arr[2000];
string s;
long long int nexl;
int32_t main() {
  cin >> n;
  for (long long int i = 0; i < n; ++i) {
    cin >> a;
    arr[i] = a;
  }
  nexl = 97;
  for (long long int i = n - 1; i >= 0; i--) {
    if (arr[i] > 0) {
      for (long long int j = 0; j < i + 1; ++j) {
        s.push_back((char)nexl);
      }
      for (long long int j = i; j >= 0; j--) arr[j] -= (i - j + 1);
      if (nexl == 122) nexl = 96;
      nexl++;
      i++;
    }
  }
  cout << s << endl;
}
