#include <bits/stdc++.h>
using namespace std;
const long long maxn = 200004;
const long long mod = 998244353, inf = 1000000007;
string ans;
long long n;
int main() {
  cin >> n;
  for (long long i = 1; n >= i; i *= 26) n -= i, ans.push_back('a');
  for (long long i = ans.size() - 1; i >= 0 && n; --i) {
    ans[i] = char(n % 26 + 'a');
    n /= 26;
  }
  cout << ans;
  return 0;
}
