#include <bits/stdc++.h>
int main() {
  int32_t n;
  std::cin >> n;
  int32_t* arr = new int32_t[n];
  for (int32_t i = 0; i < n; i++) {
    std::cin >> arr[i];
  }
  std::string ans = "";
  char last = 'b';
  for (int32_t i = n - 1; i >= 0; i--) {
    if (arr[i] == 0) continue;
    int32_t length = i + 1;
    for (int32_t j = 0; j < arr[i]; j++) {
      ans += std::string(length, last);
      last = last == 'a' ? 'b' : 'a';
    }
    for (int32_t j = i - 1; j >= 0; j--) arr[j] -= arr[i] * (i - j + 1);
  }
  std::cout << ans;
  return 0;
};
