public static String shitWordN(String s,int n){
		if(s!=null && n >= 0 && n <= s.length()){
			char[] shit =  s.toCharArray();
			reverseChar(shit,0,n-1);
			reverseChar(shit,n,s.length()-1);
			reverseChar(shit,0,s.length()-1);
			return new String(shit);
		}
		return null;
	}