#include <bits/stdc++.h>
using namespace std;
int C[2005];
int main() {
  int N;
  cin >> N;
  for (int i = 0; i < N; i++) {
    scanf("%d", &C[i]);
  }
  vector<int> Ans;
  for (int i = N - 1; i >= 0; i--) {
    int cur = C[i];
    int len = i + 1;
    for (int j = 0; j < Ans.size(); j++) {
      cur -= Ans[j] - len + 1;
    }
    for (int j = 0; j < cur; j++) {
      Ans.push_back(i + 1);
    }
  }
  for (int i = 0; i < Ans.size(); i++) {
    char c = ('a' + int(i % 26));
    for (int j = 0; j < Ans[i]; j++) cout << c;
  }
  return 0;
}
