#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
int dp[maxn];
int main() {
  int k;
  dp[1] = 0;
  for (int i = 2; i < maxn; i++) {
    dp[i] = dp[i - 1] + i - 1;
  }
  cin >> k;
  if (k == 0) cout << "a" << endl;
  int cnt = 0;
  for (int i = 2; i < maxn; i++) {
    if (k < dp[i]) {
      cnt = i - 1;
      break;
    }
  }
  char p[26] = "abcdefghigkmnopqrstuvwxyz";
  int cc = 0;
  while (k) {
    k -= dp[cnt];
    for (int i = 0; i < cnt; i++) cout << p[cc];
    cc++;
    while (1) {
      if (dp[cnt] > k)
        cnt--;
      else
        break;
    }
  }
  cout << endl;
  return 0;
}
