#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n;
  scanf("%lld", &n);
  ;
  string alpha = "abcdefghijklmnopqrstuvwxyz";
  string ans = "";
  while (n > 0) {
    n--;
    ans += alpha[n % 26];
    n /= 26;
  }
  reverse(ans.begin(), ans.end());
  cout << ans << "\n";
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
