import java.util.*;

public class Main {
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    }
} Main public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    } main {
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long N = sc.nextLong(); N sc.nextLong() sc.nextLong sc long now = 0; now 0 int keta = 1; keta 1 while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	} N > now N now {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	} now = now + (long)Math.pow(26,keta) now now + (long)Math.pow(26,keta) now (long)Math.pow(26,keta) Math.pow Math 26 keta keta++ keta keta-- keta now = now - (long)Math.pow(26,keta) now now - (long)Math.pow(26,keta) now (long)Math.pow(26,keta) Math.pow Math 26 keta long shou = N-now-1; shou N-now-1 N-now-1 N now 1 long[] name = new long[keta]; name new long[keta] keta for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	} int i=keta-1; int i=keta-1; i keta-1 keta 1 i>=0 i 0 i-- i-- i {
	    name[i] = shou % 26;
	    shou = shou/26;
	} {
	    name[i] = shou % 26;
	    shou = shou/26;
	} name[i] = shou % 26 name[i] name i shou % 26 shou 26 shou = shou/26 shou shou/26 shou 26 char[] abc = {'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'}; abc {'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'} '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' for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	} int i=0; int i=0; i 0 i<keta i keta i++ i++ i {
	    System.out.print(abc[(int)name[i]]);
	} {
	    System.out.print(abc[(int)name[i]]);
	} System.out.print(abc[(int)name[i]]) System.out.print System.out System System.out abc[(int)name[i]] abc (int)name[i] name i String[] args args public class Main {
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    }
} public class Main {
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	long now = 0;
	int keta = 1;
	while(N > now) {
	    now = now + (long)Math.pow(26,keta);
	    keta++;
	}
	keta--;
	now = now - (long)Math.pow(26,keta);
	long shou = N-now-1; //その桁の初めから何番目か
	long[] name = new long[keta];
	for (int i=keta-1;i>=0;i--) {
	    name[i] = shou % 26;
	    shou = shou/26;
	}
	char[] abc = {'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'};
	for (int i=0;i<keta;i++) {
	    System.out.print(abc[(int)name[i]]);
	}
    }
}
