#include <stdio.h>

int main(void) {
	long long int n;
	char s[20] = {0};
	int i;
	scanf("%lld", &n);

	s[0] = n % 26 + 'A';
	n /= 26;
	i = 1;
	do {
		s[i] = n % 26 + 'A' - 1;
		n /= 26;
		i++;
	}while(n > 0);
	s[i] = '\0';
	//printf("%s\n", s);
	i--;
	do {
		printf("%c", s[i]);
		i--;
	}while(i >= 0);
	printf("\n");

	return 0;
}