#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
const long long INFF = 1e18;
const int MAXN = 510;
const int MOD = 1e9 + 7;
const double PI = acos(-1.0);
const double INFD = 1E9;
const double EPS = 1e-9;
string fnd(long long n) {
  string ret = "";
  while (n) {
    int tmp = n % 26;
    if (tmp == 0) tmp = 26;
    ret += 'a' + tmp - 1;
    n /= 26;
    if (tmp == 26) --n;
  }
  reverse(ret.begin(), ret.end());
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  cout << fnd(n) << endl;
  return 0;
}
