#include <bits/stdc++.h>
const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f3fLL;
const int MOD = int(1e9) + 7;
using namespace std;
using pii = pair<int, int>;
long long gcd(long long x, long long y) {
  if (x < y) swap(x, y);
  long long r = x % y;
  while (r != 0) {
    x = y;
    y = r;
    r = x % y;
  }
  return y;
}
long long lcm(long long x, long long y) {
  long long a = x * y;
  return (a / gcd(x, y));
}
signed main(void) {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  long long n;
  cin >> n;
  stack<char> ans;
  while (n > 0) {
    ans.push('a' + (n % 26 - 1));
    n /= 26;
  }
  while (!ans.empty()) {
    cout << ans.top();
    ans.pop();
  }
  cout << '\n';
  return 0;
}
