public void printArr(String[] arr, int from, int to) {
        System.out.print("(");
        for(int i=from; i<to; i++) {
            System.out.print(arr[i]);
            if(i != to-1) {
                System.out.print(",");
            }
        }
        System.out.print(")");
    }

    public
 
 void swap(String[] points, int i, int j) {
        String temp = points[i];
        points[i] = points[j];
        points[j] = temp;
    }
    public void combination(String[] points, final int n) {
        final int m = points.length;
        String[] copyPoints = Arrays.copyOf(points, m);
        int
 
 len = m;
        int start = 0;
        int end = n-1;
        int toDelete = end-1;
        for(int i=0; len>=n; i++) {

            for(int toSwap = end+1; toSwap <= len; toSwap++) {
                printArr(copyPoints, 0, end+1);
                if(toSwap < len) {
                    swap(copyPoints, end, toSwap);
                }
            }
            System.out.println();

            if
 
(len == n) {
                copyPoints = Arrays.copyOfRange(points, start,m);
                len = copyPoints.length;
                toDelete--;
            }else {
                Arrays.sort(copyPoints);
            }
            System.out.println("toDelete="+toDelete);
            if(toDelete < 0) {
                return;
            }
            len = delete(copyPoints, len, toDelete);
            if(toDelete == 0) {
                toDelete = end-1;
                start++;
            }
//            printArr(copyPoints, 0, len);
//            System.out.print(" : ");


        }
    }
    public int delete(String[] arr, int len, final int index) {
        for(int i=index; i<len-1; i++) {
            arr[i] = arr[i+1];
        }
        return len-1;
    }