#include <bits/stdc++.h>
using namespace std;
const int dx[8] = {0, -1, 0, 1, 1, -1, -1, 1};
const int dy[8] = {-1, 0, 1, 0, -1, -1, 1, 1};
const long long mod = 1000000007;
const int base = 311;
const int N = 2005;
int n, c[N], b[N];
void gogo() {
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> c[i];
    b[i] = c[i];
  }
  for (int i = n; i >= 1; --i) {
    for (int j = i - 1; j >= 1; --j) {
      b[j] -= b[i] * (i - j + 1);
    }
  }
  int cnt = 0;
  for (int i = n; i >= 1; --i) {
    for (int j = 1; j <= b[i]; ++j) {
      for (int k = 1; k <= i; ++k) cout << char(cnt + 'a');
      cnt = (cnt + 1) % 26;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  if (fopen("sol"
            ".inp",
            "r")) {
    freopen(
        "sol"
        ".inp",
        "r", stdin);
    freopen(
        "sol"
        ".out",
        "w", stdout);
  }
  gogo();
}
