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

int main() {
	long long int N, M;
	cin >> N;
	M = 26;
	string S;

	if( N == 0 ) {
		S = 'A';
	}
	while( N ) {
		S += (N % M) + 'A';
		N /= M;
		M = 27;
	}
	reverse( S.begin(), S.end() );
	if( S.size() > 1 ) {

		S[0]--;
	}
	cout << S << endl;
}