#include <bits/stdc++.h>
using namespace std;
const int MAXN = 0;
int K;
int main() {
  scanf("%d", &K);
  for (int i = 0; i < (int)26; i++) {
    int sum = 0;
    int cnt = 1;
    while (sum <= K) {
      sum += cnt;
      cnt++;
    }
    cnt--;
    sum -= cnt;
    cnt--;
    K -= sum;
    for (int j = 0; j < (int)cnt + 1; j++) printf("%c", 'a' + i);
    if (K == 0) break;
  }
  printf("\n");
}
