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

void numberToExcelTitle(int n)
{
    if(n <= 0)
    {
        return;
    }
    char title[100];
    int index = 0;
    while (n > 0)
    {
        n--;
        title[index++] = (n % 26) + 'A';
        n /=26;
    }
    title[index] = '\0';
    for(int i= index -1; i>=0;i--)
    {
        putchar(title[i])
    }
    putchar('\n');
    
}
int main()
{
    int n;
    if(scanf("%d" , &n) <=0)
    {
        printf("Invalid input");
        return 1;
    }
    if(n<=0){
        printf("-1");
        return 1;
    }
    numberToExcelTitle(n);
    return 0;
}