#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  cin >> n;
  if (n == 0) {
    printf("a");
    return 0;
  }
  for (char c = 'a'; c <= 'z' && n; c++) {
    int sum = 0, i;
    for (i = 0; i <= n; i++) {
      n -= i;
      cout << c;
    }
  }
  printf("\n");
  return 0;
}
