#include<bits/stdc++.h>
using namespace std;
long long n; 
string s;
int main(){
    cin >> n;
    while(n > 0){
    	int t = n % 26;
    	t += 65;
    	s += t;
    	n /= 26;
	}
	for(int i = s.size() - 1;i >= 0;i--){
		cout << s[i];
	}
	return 0;
}