#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;

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

int main(){
  ll n;
  cin>>n;
    
  vector<char> A;
  
  ll p=26;
  A.push_back(char(n%26+'A'));
  n-=p;
  
  while(n>=0){
    A.push_back(char((n/p)%26+'A'));
    p*=26;
    n-=p;
  }
  reverse(ALL(A));
  rep(i,A.size()) cout<<A[i];
  cout<<endl;
    
  return 0;
}