#include<iostream>=
#include<string>

using namespace std;

int main(){

	long long N;
	long long waru=1;
	string ans="";

	cin>>N;

	while(N!=0) ans+=(char)(N%26+'A'),N/=26;

	for(int i=ans.size()-1;i>=1;i--) cout<<(char)(ans[i]-1);
	cout<<ans[0]<<endl;
}