#include <iostream>
#include <string>
#include <cmath>
using namespace std;
int main(){
  int N=0;cin>>N;
  string s1;
  int cn1=97;
  while(1){
    int M=sqrt(N);
    char c1=cn1;
    string s2;
    s2+=c1;
    int f=1;
    for(int i=1;i<M;++i){
      int cn2=cn1;
      if(f==1) cn2+=1;
      char c=cn2;
      s2.insert(s2.begin(),c);
      s2+=c;
      f*=-1;
    }
    s1+=s2;
    N-=M*M;
    if(N==1){
      char c=cn1+1;
      s1+=c;
      break;
    } else if(N==0){
      break;
    }
    cn1+=2;
  }
  cout<<s1<<endl;
}