Fisherman's net
To supplement his family income, Seva sometimes engages in industrial fishing. Modern fishermen, especially those at sea, are quite different from those at the end of the last century. They now have access to advanced computer fish finders that can detect fish underwater and display their coordinates.
Having located a school of fish on the fish finder's screen, Seva is trying to determine the minimum length of net required to catch the entire school. Assume the fish are stationary, having just eaten. Seva can use nets of any size, but all nets are available only in lengths that are multiples of 10 meters, as that's the only type sold at the underground Kryland market. The nets are made with cutting-edge technology, allowing them to bend at any angle without losing strength.
Help Seva quickly calculate the minimum length of net he needs to deploy before the fish wake up and swim away.
Input
The first line contains the number of fish detected by the fish finder N (1 ≤ N ≤ 20000). Each of the following N lines contains two integers, representing the coordinates of each fish x_i and y_i. The coordinates are within 10000 in absolute value.
Output
Output a single number: the minimum length of the net Seva needs to cast to catch the school.