import java.util.Scanner;

public class No_327 {
public static void main(String[] args) {
	String[] Alf = {"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"};
	long[] L = new long[26];
	Scanner sc = new Scanner(System.in);
	long N = sc.nextLong();
	sc.close();
	long A = N;
	long B = N;
	int C = 0;
	String ans = "";
	if(N>=26){
	while(A>=26){
		A /= 26;
		C++;
	}
		for(int i = 0; i < C; i++){
				L[i] = B % 26;
				B /= 26;
		}
			ans+= Alf[(int)B-1];
			for(int j = C-1; j >= 1; j--){
				ans += Alf[(int)L[j]-1];
			}
			ans+= Alf[(int)L[0]];
	}else{
		ans = Alf[(int)N];
	}
		System.out.println(ans);
		}
}