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

public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	}
} import java.math.BigInteger; BigInteger java.math import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	} main {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) BigInteger n = new BigInteger(sc.next()); n new BigInteger(sc.next()) String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"}; cds new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"} BigInteger index = BigInteger.valueOf(26); index BigInteger.valueOf(26) BigInteger.valueOf BigInteger 26 BigInteger nextVal = n; nextVal n int exact = 0; exact 0 StringBuilder ans = new StringBuilder(); ans new StringBuilder() BigInteger border = BigInteger.ONE; border BigInteger.ONE BigInteger BigInteger.ONE while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		} true {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		} n = n.subtract(BigInteger.ONE) n n.subtract(BigInteger.ONE) n.subtract n BigInteger.ONE BigInteger BigInteger.ONE nextVal = n.divide(index) nextVal n.divide(index) n.divide n index exact = n.mod(index).intValue() exact n.mod(index).intValue() n.mod(index).intValue n.mod(index) n.mod n index ans.insert(0, cds[exact]) ans.insert ans 0 cds[exact] cds exact if (nextVal.equals(BigInteger.ZERO)) {
				break;
			} nextVal.equals(BigInteger.ZERO) nextVal.equals nextVal BigInteger.ZERO BigInteger BigInteger.ZERO {
				break;
			} break; n = nextVal n nextVal 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) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	}
} public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	}
} Main
import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		BigInteger n = new BigInteger(sc.next());
		String[] cds = new String[]{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"};
		
		BigInteger index = BigInteger.valueOf(26);
		BigInteger nextVal = n;
		int exact = 0;
		StringBuilder ans = new StringBuilder();
		BigInteger border = BigInteger.ONE;
		
		while (true) {
			n = n.subtract(BigInteger.ONE);
			nextVal = n.divide(index);
			exact = n.mod(index).intValue();
			
			ans.insert(0, cds[exact]);
			
			if (nextVal.equals(BigInteger.ZERO)) {
				break;
			}
			n = nextVal;
		}
		System.out.println(ans);
	}
}
