#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <string.h>
#include <vector>
using namespace std;

#define ll long long
#define INF (1 << 30)
#define INFLL (1LL << 60)

#define FOR(i,a,b) for(ll i = (a);i<(b);i++)
#define REP(i,a) FOR(i,0,(a))
#define MP make_pair

int main() {
	ll n;
	cin >> n;
	ll ans[100] = {}, how = 0;
	bool flag = false;
	if(n == 0){
		ans[0] = 0;
		how = 1;
	}
	while(n != 0){
		if(flag && n > 0) n--;
		flag = true;
		ans[how] = n % 26;
		n /= 26;
		if(n > 0) n;
		how++;
	}
	for(int i = how - 1;i >= 0;i--){
		if(ans[i] == 0) cout << 'A';
		else cout << (char)('A' + ans[i]);
	}
	cout << endl;
	return 0;
}