import java.util.Scanner;
import java.util.Stack;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long N = scan.nextLong();
		
		if(N < 26) {
			System.out.println((char)(N+'A'));
		} else {
			Stack<Long> stack = new Stack();
			long value = N;
			while(true) {
				long tmp1 = value / 26;
				long tmp2 = value % 26;
				stack.push(tmp2);
				if(tmp1 <= 26) {
					stack.push(tmp1);
					break;
				}
				value = tmp1;
			}
			
			while(!stack.empty()) {
				Long v = stack.pop();
				int n = stack.size();
					
				if(n>=2){
					if(stack.peek() == 0) {
						v--; 
					}
				}
				
				if(n>=1) {
					if(v == 0) {
						v=25L;
					} else { 
						v--; 
					}
				}

				System.out.print((char)(v + 'A'));
			}
			System.out.println();
		}
	}
}