Please tell me where is the compilation error !
#include<stdio.h>
#include<math.h>
#define TG(x1,y1,x2,y2) ((y2)-(y1))/((x2)-(x1))
#define EUCLID(x1,y1,x2,y2)\
 sqrt(((x2)-(x1))*((x2)-(x1))+((y2)-(y1))*((y2)-(y1)))
#define INFINIT 100000
#define MAX 102
struct POINT
    {float x,y;};
int N,i;
float R,rope,m1,m2,m,rad;
struct POINT p[MAX];
void main(void)
 {
  scanf("%d%f",&N,&R);
  for(i=0;i<N;i++)
   scanf("%f%f",&p[i].x,&p[i].y);
  p[N]=p[0];
  p[N+1]=p[1];
  switch (N)
   { case 1 : {rope=2*M_PI*R;break;}
     case 2 : {rope=2*M_PI*R+2*EUCLID(p[0].x,p[0].y,p[1].x,
p[1].y);break;}
     default : {
    rope=0.0;
    if (p[0].x!=p[1].x)
      m1=TG(p[0].x,p[0].y,p[1].x,p[1].y);
    else
    m1=INFINIT;
    for(i=1;i<=N;i++)
     { rope+=EUCLID(p[i].x,p[i].y,p[i+1].x,p[i+1].y);
       if (p[i].x!=p[i+1].x)
        m2=TG(p[i].x,p[i].y,p[i+1].x,p[i+1].y);
       else
        m2=INFINIT;
       if (fabs(m2-m1)==INFINIT)
        rad=M_PI_2;
       else
        {
         if (m1==INFINIT && m2!= INFINIT)
          m= -1.00/m2;
         else if (m2==INFINIT && m1!= INFINIT)
           m=1.00/m1;
         else
          m=(m2-m1)/(1+m1*m2);
         rad=atan(m);
         if (rad<=0)
          rad+=M_PI;
        }/*else*/
      rope+=R*rad;
      m1=m2;
      }/*for*/
      }/* default*/
     }/*switch*/
   printf("%.2f",rope);
   }/*main*/