#include <stdio.h>
#include<string.h>
int main()
{
    long long n;
    if(scanf("%lld", &n) !=1 || n>=1000000 || n<=-1000000 || !isalpha)
    {
        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;
}