import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	}

} import java.math.BigInteger; BigInteger java.math import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	}

} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	} main {
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) BigInteger dogs = new BigInteger(String.valueOf(sc.next())); dogs new BigInteger(String.valueOf(sc.next())) BigInteger[] results; results StringBuilder result = new StringBuilder(""); result new StringBuilder("") results = dogs.divideAndRemainder(new BigInteger("1")) results dogs.divideAndRemainder(new BigInteger("1")) dogs.divideAndRemainder dogs new BigInteger("1") while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		} results[0].compareTo(new BigInteger("0")) != 0 results[0].compareTo(new BigInteger("0")) results[0].compareTo results[0] results 0 new BigInteger("0") 0 {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		} dogs = dogs.subtract(new BigInteger("1")) dogs dogs.subtract(new BigInteger("1")) dogs.subtract dogs new BigInteger("1") results = dogs.divideAndRemainder(new BigInteger("26")) results dogs.divideAndRemainder(new BigInteger("26")) dogs.divideAndRemainder dogs new BigInteger("26") dogs = results[0] dogs results[0] results 0 result.insert(0,(char)('a' + (char)results[1].intValue())) result.insert result 0 (char)('a' + (char)results[1].intValue()) 'a' (char)results[1].intValue() results[1].intValue results[1] results 1 System.out.println(result.toString()) System.out.println System.out System System.out result.toString() result.toString result String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	}

} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	}

} Main
import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		BigInteger dogs = new BigInteger(String.valueOf(sc.next()));
		BigInteger[] results;
		StringBuilder result = new StringBuilder("");

		results = dogs.divideAndRemainder(new BigInteger("1"));
		while(results[0].compareTo(new BigInteger("0")) != 0) {
			dogs = dogs.subtract(new BigInteger("1"));
			results = dogs.divideAndRemainder(new BigInteger("26"));
			dogs = results[0];
			result.insert(0,(char)('a' + (char)results[1].intValue()));
		}

		System.out.println(result.toString());

	}

}