#include <iostream>
#include <stack>
using namespace std;

int main() {
	// your code goes here
	long long int a;
	std::cin>>a;
	std::stack<char> stc;
	
	while(a>=0){
		stc.push(a%26+'A');
		a/=26;
		a--;
	}
	while(stc.empty()==false){
		std::cout<<stc.top();
		stc.pop();
	}
	return 0;
}