#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 200003
#define MOD 1000000007
#define INF 1000000000000000000

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