#include <bits/stdc++.h>
int main() {
  int n;
  char ch = 'a';
  scanf("%d", &n);
  int arr[n + 1];
  arr[0] = 0;
  for (int i = 0; i < n; i++) scanf("%d", &arr[i + 1]);
  int q;
  for (int i = n; i >= 1; i--) {
    while (arr[i] > 0) {
      for (int j = 1; j <= i; ++j) {
        printf("%c", ch);
      }
      ch = ((ch + 1 - 'a') % 26) + 'a';
      for (int k = 1; k < i; k++) {
        arr[k] -= (i - k + 1);
      }
      arr[i]--;
    }
  }
  return 0;
}
