#include <bits/stdc++.h>
int a[3000];
char ans[3000];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &a[i]);
  a[n] = 0;
  int ind = 0, bit = 0;
  int cur_count = 0;
  for (int len = n - 1; len >= 0; len--) {
    int plus = a[len] - (a[len + 1] + cur_count);
    for (int i = 0; i < plus; i++) {
      for (int j = 0; j < len + 1; j++, ind++) ans[ind] = 'a' + bit;
      bit = (bit + 1) % 2;
    }
    cur_count += plus;
  }
  for (int i = 0; i < n; i++) printf("%c", ans[i]);
}
