#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
typedef long long ll;
int main(){
  ll n;
  cin>>n;
  string s;
  int f=0;
  while(1){
    ll a=n%26;
    if(f==1) a-=1;
    a+=65;
    char b=a;
    s+=b;
    n/=26;
    if(n==0) break;
    f=1;
  }
  reverse(s.begin(),s.end());
  cout<<s<<endl;
  return 0;
}