#include<bits/stdc++.h>
using namespace std;
long long n;
string s;
int main(){
	cin>>n;
	n=n+1;
	while(n--){
		char g=char(n%26+65);
		//cout<<g<<endl;
		s=s+g;
		n/=26;
	}
	reverse(s.begin(),s.end());
	cout<<s;
	return 0;
}