public class Solution {
    public static void main(String[] args) {
        System.out.println(getPartOfString("JavaRush - лучший сервис обучения Java."));
    }

    public static String getPartOfString(String string) {

        int indexStart = 0;
        int indexLast = 0;
        int spaceCount = 0;

        char[] array = string.toCharArray();
        for (int i = 0; i < array.length; i++) {
            if (array[i] == ' ') {
                spaceCount++;
            }
        }

        if (string.isEmpty() && spaceCount >= 4) {
            spaceCount = 0;

            for (int i = 0; i < array.length; i++) {
                if (array[i] == ' ') {
                    indexStart = i + 1;
                    break;
                }
            }

            for (int i = 0; i < array.length; i++) {
                if (array[i] == ' ') {
                    spaceCount++;
                    if (spaceCount == 5) {
                        indexLast = i;
                        break;
                    }
                }
            }

        } else if (spaceCount < 4) new TooShortStringException();

        String str = "\"" + string.substring(indexStart, indexLast) + "\"" ;

        return str;
    }

    public static class TooShortStringException extends RuntimeException{
    }
}