#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>

#define MOD 1000000007
#define pe(str) return cout<<(str)<<endl,0
#define px(str) {cout<<(str)<<endl;exit(0);}
#define pr(str) cout<<(str)<<endl
#define prpr(str) cout<<str<<endl
#define db(str) cerr<<(str)<<endl
#define dbdb(str) cerr<<str<<endl
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
#define spr(a) setprecision(a)
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;

template<class InputIterator>
void dump(InputIterator first,InputIterator last,char delim=' '){
	for(InputIterator it=first;it!=last;it++){
		if(it!=first)cout<<delim;
		cout<<*it;
	}
}


ull p(ull x,ull y){
	if(y==0) return 1;
	ull A=p(x,y/2)%MOD;
	return (y&1?((A*A)%MOD*x)%MOD: (A*A)%MOD);
	// return (y&1?((A*A)*x):(A*A));
}

int main(void){
	ll n;
	std::vector<int> v;
	ll k=1;
	cin>>n;
	// if(n==0)pe("A");
	while(n>=k*26)k*=26;
	for(ll i=k;i>=1;i/=26){
		v.push_back(n/i);
		n%=i;
	}
	re(i,v.size()){
		if(i==0)cout<<(char)('A'+v[i]-1);
		else cout<<(char)('A'+v[i]);
	}
	cout<<endl;
	return 0;
}