/* -*- coding: utf-8 -*-
 *
 * 327.cc: No.327 アルファベット列 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

int main() {
  ll n;
  cin >> n;

  int k = 1;
  ll d = 26;
  while (n >= d) n -= d, d *= 26, k++;
  //printf("k=%d, n=%lld\n", k, n);

  string ans(k, ' ');

  for (int i = k - 1; i >= 0; i--) {
    ans[i] = 'A' + (n % 26);
    n /= 26;
  }

  cout << ans << endl;
  return 0;
}