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