#include<bits/stdc++.h>
using namespace std;
long long n; 
string s = "";
int main(){
    cin >> n;
    if(n <= 25){
    	cout << char(n + 65);
	}
	else{
		n++;
        while(n > 0){
    	    int t = n % 26;
    	    t += 64;
    	    if(t <= 64) 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;
}