import java.util.*;
import java.io.PrintWriter;

public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	}
} import java.util.*; util.* java import java.io.PrintWriter; PrintWriter java.io public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	}
} Main public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	} main {
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) long n=sc.nextLong(); n sc.nextLong() sc.nextLong sc long ts=26; ts 26 int count=0; count 0 while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		} n-ts>0 n-ts n ts 0 {
			count++;
			n-=ts;
			ts*=26;
		} count++ count n-=ts n ts ts*=26 ts 26 StringBuilder ans=new StringBuilder(); ans new StringBuilder() ts/=26 ts 26 n-- n for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		} int i=0; int i=0; i 0 i<count+1 i count+1 count 1 i++ i++ i {
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		} {
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		} ans.append((char)('a'+n/ts)) ans.append ans (char)('a'+n/ts) 'a' n/ts n ts n%=ts n ts ts/=26 ts 26 System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	}
} public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	}
} Main
import java.util.*;
import java.io.PrintWriter;

public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ts=26;
		int count=0;
		while(n-ts>0){
			count++;
			n-=ts;
			ts*=26;
		}
		StringBuilder ans=new StringBuilder();
		ts/=26;
		n--;
		for(int i=0; i<count+1; i++){
			ans.append((char)('a'+n/ts));
			n%=ts;
			ts/=26;
		}
		System.out.println(ans);
	}
}
