#include<iostream>
#include<string>
#include<cmath>

int main() {
	const char alpha[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	std::string ans;
	long long n;
	std::cin >> n;

	int p = 0;
	while (n >= pow(26, p + 1)) {
		n -= pow(26, p + 1);
		p++;
	}

	while (p >= 0) {
		long long num = static_cast<long long>(pow(26, p));
		ans += alpha[n / num];
		n -= n / num * num;
		p--;
	}
	std::cout << ans << std::endl;
	return 0;
}