#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    long long N;
    cin >> N;
    string ans;
    
    long long x = 0;
    int i;
    for ( i = 1; i < 10; i++ ) {
        long long a = 1;
        for ( int j = i; j > 0; j-- ) {
            a *= 26;
        }
        x += a;
        
        if ( x > N ) { break; }
    }
    
    for ( ; i > 1; i-- ) {
        long long a = 1;
        for ( int j = i-1; j > 0; j-- ) {
            a *= 26;
        }
        
        ans += 'A' + (N / a) - 1;
        N -= (N / a)*a;
        
    }
    ans += 'A' + (N%26);
    
    cout << ans << endl;
    
    return 0;
}