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