Rokua a long rope around a nail

Background

There are n cylindrical large nails on the plane, the radius is r, and all the nails form a convex polygon.

Now you're going to surround these nails with a rope, and the rope's diameter is negligible.

Describe

Find out the length of the rope

Format input Format

Line 1th two number: integer N (1<=n<=100) and real R.

The next n lines give the coordinates of the center of N Nails in a counterclockwise order
The absolute value of the coordinate does not exceed 100.

Output format

A number, the length of the rope, exactly 2 digits after the decimal point.

Example 1 Sample Input 1

4 1

0.0 0.0

2.0 0.0

2.0 2.0

0.0 2.0

Sample Output 1

14.28

Limit

Each test point 1s

Tips

If you're using a more complex method of AC, think about whether there's a simpler way.

Find the law, no matter how much n is the distance between his two points plus a circle can draw their own.

#include <iostream>#include<cstring>#include<cstdio>#include<cmath>using namespacestd;Const DoublePi=acos (-1.0);intI,j,n;Doubler,x[101],y[101],ans;intMain () {scanf ("%D%LF",&n,&s);  for(i=0; i<n;++i) {scanf ("%LF%LF",&x[i],&Y[i]); if(i>=1) Ans+=sqrt ((x[i]-x[i-1]) * (x[i]-x[i-1]) + (y[i]-y[i-1]) * (y[i]-y[i-1])); if(i==n-1) Ans+=sqrt ((x[i]-x[0]) * (x[i]-x[0]) + (y[i]-y[0]) * (y[i]-y[0])); } ans+=r*2*Pi; printf ("%.2LF", ans);}

Rokua a long rope around a nail