public static int beautifulDays(int i, int j, int k) {
        int count = 0;
        
        for (int day = i; day <= j; day++) {
            if (Math.abs(day - reverse(day)) % k == 0) count++;
        }

        return count;
    }

static int reverse(int n) {
        StringBuilder sb = new StringBuilder(String.valueOf(n));
        
        return Integer.parseInt(sb.reverse().toString());
    }