#include <bits/stdc++.h>
using namespace std;
int n, a[2005];
string s;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  int l = 0;
  bool b = 0;
  for (int i = n; i >= 1; i--) {
    int cur = a[i] - (a[i + 1] + l);
    for (int j = 0; j < cur; j++) {
      for (int k = 0; k < i; k++) s += (b ? 'b' : 'a');
      b = !b;
    }
    l += cur;
  }
  cout << s << endl;
}
