#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

#define int ptrdiff_t
#define div lldiv
#define div_t lldiv_t

int N;
char buf[1024];

main(){
    scanf("%td\n", &N);
    char *p = buf+1000;
    N++;
    while (N--) {
        div_t d = div(N, 26);
        *--p = (d.rem + 'A');
        N = d.quot;
    }
    puts(p);
    return 0;
}