#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long

signed main(){

  int n; cin >> n;
  n++;

  string ans;
  while(n > 0){
    ans += (char)('A' + (n-1) % 26);
    n /= 26;
  }
  reverse(ans.begin(),ans.end());
  cout << ans << endl;

  return 0;
}