#include <stdio.h>
int main()
{
    long long n;
    
    if(scanf("%lld", &n) !=1 || n>=1000000 || n<=-1000000 || !isalph) 
    {
        printf("Invalid Input");
        return 0;
    }
    if(n <= 0) {
        printf("-1");
        return 0;
    }
    char result[27];
    int index = 0;
    
    while (n > 0) {
        n--;
        int remainder = n % 26;
        result[index++] = 'A' + remainder;
        n /= 26;
    }
    for(int i = index - 1; i >= 0; i--) {
        printf("%c", result[i]);
    }
    
    return 0;
}