#include<iostream>
using namespace std;
long long n, m = 0; 
char a[55];
int main(){
	cin >> n;
	n++;
	while(n)
	{
		n--;
		a[m++] = n % 26 + 'A';
		n /= 26;
	}
	for(int i = m - 1; i >= 0; i--)
	{
		cout << a[i];
	}		
	cout << "\n";
	
	return 0;
}