#include <stdio.h>
#include<stdlib.h>

void convertTOTittle(int n) {
    if (n < 0) {
       printf("-1\n");
       return;
    }
    
    char result[100];
    int index = 0;
    
    while (n > 0){
        n--;
        int remainder = n % 26;
        result[index++] = 'A' + remainder;
        n /= 28;
    }
    for (int i = index - 1; i >= 0; i--) {
        printf("%c", result[i]);
    }
    printf("\n");
    
    
}
int main() {
    int n;
    if (scanf("%d", &n) != 1) {
        printf("Invalid Input\n");
    }else {
        converTOTitle(n);
    }
    return 0;
}