#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]);
    }
    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;
}