#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  long long n;
  cin >> n;

  long long base = 26;
  int len = 1;
  while (n >= base) {
    n -= base;
    base *= 26;
    ++len;
  }

  string s;
  REP (i, len) {
    s += char('A' + (n % 26));
    n /= 26;
  }
  reverse(ALL(s));
  cout << s << endl;
  
  return 0;
}