#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>

using namespace std;

#define INF 		2000000007
#define MOD			1000003

#define MAX 		105

#define REP(i,n)	for(int i=0;i<(n);++i)
#define REPS(i,s,t)	for(int i=(s);i<(t);++i)

typedef unsigned int 			uint;
typedef unsigned long long int	ull;
typedef long long int ll;

int DP[20005];

char itoc(int n){
	return (char)'A'+n;
}

int main(){
	ll N;cin>>N;

	#define AMAX	26
	vector<char> ans;
	while(N>=0){
		ans.push_back(itoc(N%AMAX));
		N=N/AMAX-1;
	}
	for(int i=ans.size()-1;i>=0;--i)
		cout <<ans[i];
	cout << endl;

	return 0;
}