void quick_sort(int *a, int left, int right){
	if(left>right) return;
	int pivot = a[left];
	int temp, i=left, j=right;
	while(i!=j){
		while(a[j]>=pivot&&j>i) j--;
		while(a[i]<=pivot&&i<j) i++;
		if(i<j){
			temp = a[i];
			a[i] = a[j];
		a[j] = temp;
		}
	}
	a[left] = a[i];
	a[i] = pivot;
	quick_sort(a,left,i-1);
	quick_sort(a,i+1,right);
}