#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

vector<int> q;

int main()
{
	ll N;
	cin >> N;
	
	if (N < 26) {
		printf("%c\n",'A'+N);
		return 0;
	}

	while (N / 26 != 0) {
		if(N/26 -1 < 26)
		q.push_back((N/26)-1);
		if(N % 26 < 26)
			q.push_back(N % 26);
		N /= 26;
	}

	for (int i = 0; i < q.size(); i++)
		printf("%c",'A'+q[i]);
	cout << endl;
	return 0;
}