#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
	ll n;
	cin >> n;
	int s[15];
	int k = 0;
	while (n>=pow(26,k+1)) {
		n -= pow(26, ++k);
	}
	int i = 0;
	while(i<=k) {
		s[i++] = n % 26;
		n /= 26;
	} 
	for (i--;i >= 0;i--) {
		char c = 'A' + s[i];
		cout << c;
	}
	cout << endl;


	return 0;
}