#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> c(n + 1);
  for (int i = 1; i <= n; ++i) cin >> c[i];
  int j = n;
  int counter = 0;
  vector<int> ans;
  while (j > 0) {
    while (j > 0 && c[j] == 0) --j;
    if (j == 0) break;
    for (int k = 0; k < c[j]; ++k) {
      for (int i = 0; i < j; ++i) ans.push_back(counter);
      counter ^= 1;
    }
    for (int i = 1; j - i > 0; ++i) {
      c[j - i] -= c[j] * (i + 1);
    }
    --j;
  }
  for (int i = 0; i < n; ++i) cout << (char)('a' + ans[i]);
  cout << endl;
  return 0;
}
