#include <bits/stdc++.h>
unsigned long long Mypow(unsigned long long x, unsigned long long n) {
  unsigned long long ret = 1;
  if (n == 0) return 1;
  while (n > 0) {
    if (n & 1) ret = ret * x;
    x = x * x;
    n >>= 1;
  }
  return ret;
}
int main() {
  long long i, n, jou = 1, cur = 0, kake = 2, tmp = 0;
  char ans[300] = {};
  scanf("%lld", &n);
  while (Mypow(26, jou) <= n) jou++;
  for (i = jou - 1; i >= 0; i--) {
    tmp = Mypow(26, i);
    while (tmp * kake <= n) kake++;
    kake--;
    ans[cur] = 'a' + kake - 1;
    n -= tmp * kake;
    kake = 2;
    cur++;
  }
  printf("%s", ans);
  return 0;
}
