#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<list>
#include<queue>
#include<stack>
#include<utility>
#include <fstream>
#include<set>
#include<map>
#include<cctype>
#include<cmath>
#include<algorithm>
#include <numeric>
using namespace std;


#define RALL(x) (x).rbegin(),(x).rend()
#define ALL(x) (x).begin(),(x).end()
#define repp(i,n) for(int (i)=1;(i)<=(n);(i)++)
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define clr(a) memset((a), 0 ,sizeof(a))
#define found(s,e) ((s).find(e)!=(s).end())

typedef pair<int,int> P;
typedef vector<pair<int,string> > pii;
typedef map<string,int> mdi;


int main(){
	long long n;
	cin >> n;
	n++;
	string res="";
	while(n>0){
		n--;
		res+=char(n%26+'A');
		n/=26;
	}
	cout << string(res.rbegin(),res.rend()) << endl;
	return 0;
}