#include <iostream>
using namespace std;
typedef long long ll;

/*
A -> 1
B -> 2
...
Z -> 26
AA -> 27 = (26 * A + A)
AB -> 28 = (26 * A + B)
...
AZ -> 52 = (26 * A + Z)
BA -> 53 = (26 * B + A)
...
ZZ -> 702 = (26 * Z + Z)
AAA -> 703 = (26^2 * A + 26 * A + A)
*/

int main(){
	ll N;
	cin >> N;
	++N;

	string res = "";
	while(N > 0){
		--N;
		res += char(N % 26 + 'A');
		N /= 26;
	}
	cout << string(res.rbegin(), res.rend()) << endl;
	return 0;
}