#include <stdio.h>

#define u_LL unsigned long long

int ori_pow(u_LL base, u_LL num, u_LL* ans)
{
	int isOver = 0;
	*ans = 1;
	u_LL i = num;
	while (num != 0) {
		if (*ans * base < *ans) {
			isOver = 1;
			break;
		}
		*ans = *ans * base;
		num--;
	}
	return isOver;
}

int main(int argc, char* argv[])
{
	char	ANS[1000] = "";
	u_LL	targetNumber = 0;
	scanf("%lld", &targetNumber);

	u_LL	max = 0;
	if (0 != ori_pow(10, 12, &max)) {
		return 0;
	}
	if (max < targetNumber) {
		return 0;
	}

	u_LL alphaCnt = 26;
	int suffix = 0;
	u_LL answer = targetNumber + 1;
	do {
		answer--;
		u_LL surplus = answer % alphaCnt;
		char alpha = 'A' + surplus;
		ANS[suffix] = alpha;
		suffix++;
		answer = answer / alphaCnt;
	} while (answer);

	for (int i = 0; i < suffix; i++) {
		printf("%c", ANS[suffix - (i + 1)]);
	}
	printf("\n");

	return 0;
}