#include <iostream>

using namespace std;

void SubtractOneFromDigit(int* data, int digit, int maxDigits);
long long Pow(long long num, int multiplier);

int main() {
	const int ALPHABET_COUNT = 26;
	
	long long n;
	cin >> n;
	
	int numberOfDigits = 1;
	while (true) {
		if (Pow(ALPHABET_COUNT, numberOfDigits) <= n)
			numberOfDigits++;
		else
			break;
	}

	int* data = new int[numberOfDigits];
	for (int multiplier = numberOfDigits - 1; multiplier > 0; multiplier--) {
		long long sub = Pow(ALPHABET_COUNT, multiplier);
		int digitNum = 0;
		while (n - sub >= 0) {
			n -= sub;
			digitNum++;
		}

		int digit = multiplier;
		data[digit] = digitNum;
	}
	data[0] = (int)n;

	int digit = 1;
	while (digit < numberOfDigits)
	{
		SubtractOneFromDigit(data, digit, numberOfDigits - 1);
		digit++;
	}
	
	int maxNumberOfDigitsIndex = 0;
	for (int i = numberOfDigits - 1; i >= 0; i--) {
		if (data[i] != -1) {
			maxNumberOfDigitsIndex = i;
			break;
		}
	}

	char alphabetTable[ALPHABET_COUNT];
	for (int i = 0; i < ALPHABET_COUNT; i++) {
		alphabetTable[i] = 'A' + i;
	}

	string output;
	for (int i = maxNumberOfDigitsIndex; i >= 0; i--) {
		int num = data[i];
		char alphabet = alphabetTable[num];
		output.push_back(alphabet);
	}

	cout << output.c_str() << endl;

	return 0;
}

void SubtractOneFromDigit(int* data, int digit, int maxDigits) {
	if (data[digit] == 0) {
		if (digit < maxDigits) {
			SubtractOneFromDigit(data, digit + 1, maxDigits);
			data[digit] = 25;
		}
		else {
			data[digit] = -1;
		}
	}
	else {
		data[digit]--;
	}
}

long long Pow(long long num, int multiplier) {
	long long ret = num;
	for (int i = 1; i < multiplier; i++) {
		ret *= num;
	}

	return ret;
}