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

  return 0;
}