#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0), cin.tie(0);
  int n;
  cin >> n;
  vector<int> c(n);
  for (int i = 0; i < n; ++i) cin >> c[i];
  string sol;
  for (int i = n - 1, a = 0; i >= 0; --i) {
    while (c[i]) {
      sol += string(i + 1, a + 'a');
      for (int j = i; j >= 0; --j) c[j] -= i - j + 1;
      a = (a + 1) % 26;
    }
  }
  cout << sol << '\n';
}
