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