#include "bits/stdc++.h"

using namespace std;

typedef long long ll;
typedef long double ld;

#define mp make_pair
#define pb push_back
#define FOR(i,a,x) for(int i=(a);i<(x);i++)
#define rep(i,n)	FOR(i,0,n)
#define xFOR(i,a,x) for(int i=(a);i<=(x);i++)
#define xrep(i,n) xFOR(i,1,n)
#define sor(v) sort(v.begin(),v.end())
#define rev(s) reverse(s.begin(),s.end())
#define lb(vec,a) lower_bound(vec.begin(),vec.end())
#define ub(vec,a) upper_bound(vec.begin(),vec.end())
#define uniq(vec) vec.erace(unique(vec.begin(),vec.end(),vec.end))
#define mp1(a,b,c) P1(a,P(b,c))
#define all(x) (x).begin(),(x).end()

#define debug(X) cout<<"["<<#X<<"]"<<X<<endl;



inline bool cheak(int x, int y, int xMax, int yMax) { return x >= 0 && y >= 0 && xMax > x && yMax > y; }
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<typename T> inline string toString(const T &a) { ostringstream oss; oss << a; return oss.str(); }
template<class T> inline T sqr(T x) { return x*x; }

const double PI = acos(-1.0);
const int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, -1, 0, 1, -1, 1, -1, 1 };
const int mod = 1000000007;
//const int INF = 1e9;
const int NIL = -1;
ll n,i;
ll keta[100000010];
string alpha="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
string alpha2= "AABCDEFGHIJKLMNOPQRSTUVWXYZ";
string res="";
bool flag = true;
int main(){
	cin >> n;
	if (n == 0) {
		cout << "A" << endl;
		return 0;
	}
	
	while (n > 0) {
		int d = n % 26;
		n /= 26;
		res = alpha[d] + res;
		if (flag) {
			alpha = 'A' + alpha;
			//flag = false;
		}
	}
	cout << res << endl;

	return 0;
}