#include<stdio.h>
#include<string.h>
#include<string.h>

void numberToExcelTitle(int n) {
    if (n <= 0) {
        return ;
    }
    char ch 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]);
    }
    putchar('\n');
}
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;
    
}