#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

signed main(){
  ll N; cin >> N;
  string ans;
  while( N ){
    ans += ( char ) ( 'A' + N % 26 );
    N /= 26; --N;
  }
  reverse( ans.begin(), ans.end() );
  cout << ans << endl;
  return 0;
}