import java.util.*;

public class No327{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();
		StringBuilder sb = new StringBuilder();
		int pow = 9;
		while((long)Math.pow(26, pow) > n){
			pow--;
		}
		for(int p = pow; p >= 0; p--){
			long div = (long)Math.pow(26, p);
			if(p == pow){
				sb.append((char)(64+n/div));
			}else{
				sb.append((char)(65+n/div));
			}
			n %= div;
		}
		
		System.out.println(sb);
	}
}