Rope#1042
Plotters barbarously hammered nails into an innocent flat surface, so that only the heads remain visible. Moreover, all nails were hammered into the vertices of a convex polygon. Then they stretched a rope around all the nails, enclosing them tightly.
Your task is to determine the length of this rope.
The first line contains two numbers: (1 \le N \le 100) — the number of nails, and a real number — the radius of the nail heads. All heads have the same radius. Each of the next lines contains two real numbers — the coordinates of the center of the next nail, separated by a space. The absolute value of each coordinate does not exceed . The nails are listed in order of traversal of the convex polygon's vertices (either clockwise or counterclockwise), starting from an arbitrary nail. Heads of different nails do not touch.
Output a real number rounded to two decimal places — the length of the rope stretched around all the nails.
Example 1