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

int main() {
    long long n;
    
    if (scanf("%lld", &n) != 1) {
        printf("Invalid");
        return 0;
    }
    
    if (n < 0) {
        printf("-1");
    else
        printf("Invalid")
        return 0;
    }
    
    char result[50];
    int index = 0;
    
    while (n > 0) {
        n--;
        
        result[index++] = (char)('A' + (n % 26));
        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", result);
    return 0;
}