#include <bits/stdc++.h>
using namespace std;
mt19937 gen(time(NULL));
const long double eps = 1e-9;
const int inf = 1e9;
const int mod = 1e9 + 7;
const long long infinity = 2 * 1e18;
inline int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
int w[100005];
int n, m;
void solve() {
  long long k;
  cin >> k;
  if (k == 0) {
    cout << "a";
    return;
  }
  int j = 0;
  while (k) {
    long long sum = 0;
    int i = 0;
    while (sum < k) sum += i, i++;
    if (sum > k) i--, sum -= i;
    for (int k = 0; k < i; k++) cout << (char)('a' + j);
    j++;
    k -= sum;
  }
  cout << '\n';
}
int main() {
  int t = 1;
  while (t--) {
    clock_t z = clock();
    solve();
    fprintf(stderr, "%.3f\n", (double)(clock() - z) / CLOCKS_PER_SEC),
        fflush(stderr);
  }
}
