#include <bits/stdc++.h>
using namespace std;
int max(int x, int y) { return x > y ? x : y; }
int min(int x, int y) { return x > y ? y : x; }
int gcd(int a, int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int main() {
  string abc = "abcdefghijklmnopqrstuvwxyz";
  string ans;
  int k;
  cin >> k;
  int len = 0, i, j;
  while (len < 26) {
    char ch = abc[len];
    int sum = 0;
    for (i = 1; sum <= k; i++) sum += i;
    for (j = 1; j < i; j++) ans += ch;
    i--;
    sum -= i;
    if (sum == k) break;
    len++;
    k -= sum;
  }
  cout << ans << endl;
  return 0;
}
