#include <iostream>
#include <stack>

using namespace std;

int main(int argc, const char* argv[])
{
	int64_t N;
	cin >> N;
	stack<char> st;
	do {
		st.push('A' + N % 26);
		N /= 26;
		N--;
	} while (N >= 0);

	while (st.size()) cout << st.top(), st.pop();
	cout << endl;
	return 0;
}