public static boolean train() {
		int max_passengers = 1;

		int[][] rides = {{0,1,1}, {1,0,0}};
//		int[][] rides = {{1,0,0}, {0,1,0}};
//		int[][] rides = {{0,1,0}, {1,0,1}};
//		int[][] rides = {{0,1,1}, {0,0,0}};

		int passengers = 0;
		for(int i = 0; i < rides.length; i++) {
			// passengers leave
			passengers -= rides[i][0];
			if(passengers < 0) return false;

			// passengers enter
			passengers += rides[i][1];
			if(passengers > max_passengers) return false;

			// if train is not filled and ppl are waiting
			if(passengers < max_passengers && rides[i][2] > 0) return false;
		}

		// all passengers should have left the train
		return passengers == 0;
	}

	public static boolean clock() {
		int[] a = {1,2,4,5,6,13};
		int[] b = new int[a.length];
		for(int i = 0; i < b.length; i++)
			b[i] = (a[i] + 1) % 360;

		Arrays.sort(a);
		Arrays.sort(b);

		System.out.println(Arrays.toString(a));
		System.out.println(Arrays.toString(b));
		System.out.println("");

		int[] dist_a = new int[a.length];
		int[] dist_b = new int[b.length];
		for(int i = 0; i < a.length; i++) {
			dist_a[i] = a[(i+1)%a.length] - a[i];
			while(dist_a[i] < 0) dist_a[i] += 360;

			dist_b[i] = b[(i+1)%b.length] - b[i];
			while(dist_b[i] < 0) dist_b[i] += 360;
		}

		for(int off = 0; off < a.length; off++) {
			boolean same = true;
			for(int i = 0; i < a.length; i++) {
				if(dist_a[i] != dist_b[(i+off)%dist_b.length]) {
					same = false;
					break;
				}
			}

			if(same) return same;
		}

		//System.out.println(Arrays.toString(dist_a));
		//System.out.println(Arrays.toString(dist_b));

		return false;
	}

	public static void explosions() {
		int[] heights = {2,1,4,1,3,4,8,1,1,10};
		Arrays.sort(heights);
		int num = heights.length;
		System.out.println(num + " : "+Arrays.toString(heights));

		int last = 0;
		int max = 0;
		for(int i = 0; i < num; i++) {
			if(heights[i] < i) {
				last = i;
				if(heights[i] > max)
					max = heights[i];
			}
		}

		System.out.println("explosions: " + (max + (num - last - 1)));
	}