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

int main(){
  unsigned long long n;
  cin>>n;
  string s;
  while(n){ //nが1以上
     n--;
     s+='a'+(n%26);
     n/=26;
  }
  reverse(s.begin(),s.end());
  cout<<s<<endl;
}
