#include<stdio.h>
#include<string.h>
int main()
{
    long long n;
    if(scanf("%lld", &n) !=1)
    {
        printf("Invalid input");
        return 0;
    }
    if(n <= 0)
    {
        printf("-1");
        return 0;
    }
    char resulr [50];
    int idx = 0;
    if (n == 0)
    {
        printf("Invalid input");
        return 0;
    }
    while(n > 0)
    {
        long long rem =(n - 1) % 26;
        result[idx++] = 'A' + rem;
        n= (n -1) /  26;
    }
    result[idx] = '\0';
    for (int i = 0; i < idx/2; i++)
    {
        char temp = result[i];
        result[i] = result[idx - 1 - i];
        result[idx - 1 - i] = temp;
    }
    printf("%s", result);
    return 0;
}