#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 result[20];
    int index=0;
    
    while(n>0)
    {
        n--;
        int rem = n%26;
        result[index++] = 'A'+rem;
        n /= 26;
    }
    result[index]='\0';
    for(int i=0;i<index/2;i++)
    {
        char temp = result[i];
        result[i] = result[index-i-1];
        result[index-i-1] = temp;
    }
    printf("%s",re)
}