My code is:

#include <iostream.h>
#include <math.h>
#define pi acos(-1)
#define lin(a,b,c) (a.x*b.y-b.x*a.y+c.y*(b.x-a.x)+c.x*(a.y-b.y))
#define eq(a,b) ((a.x==b.x && a.y==b.y)?1:0)

typedef struct {double x; double y;} P;

int n,InUse[110];
double res;
P pArr[110];

double sqr(double x) {
  return x*x;
}

double len(P a, P b) {
  return sqrt(sqr(a.x-b.x)+sqr(a.y-b.y));
}

void FindMaxPoly(void) {
  P tmp;
  int i, j;

  for (i=0,tmp=pArr[0];i<n;i++) {
    if (pArr[i].x>tmp.x) j=i;
    InUse[i]=0;
  }
  tmp=pArr[j]; InUse[j]=1;

  while (1) {
    if (eq(tmp,pArr[0])==0) j=0;
    else j=1;
    for (i=0;i<n;i++)
      if ( eq(pArr[i],pArr[j])==0 &&
           eq(pArr[i],tmp)==0 &&
           lin(tmp,pArr[j],pArr[i]) < 0
         ) j=i;
    if (InUse[j]) break;
    InUse[j]=1; tmp=pArr[j];
  }
}

/* The problem differs of ROPE one in that you have to find out
    is one P in the polygon or not!!!
*/

int main() {
  int i,r;
  P last;

  cin>>n>>r;
  for (i=0;i<n;i++) cin>>pArr[i].x>>pArr[i].y;

  FindMaxPoly();
  pArr[n]=pArr[0]; InUse[n]=1;
  res=2*pi*r;

  i=0;
  while (InUse[i]==0) i++;
  last=pArr[i];
  for (i=0;i<=n;i++)
    if (InUse[i]) {
      res+=len(last,pArr[i]);
      last=pArr[i];
    }
  cout<<floor(res);
  //cin.get(); cin.get();
  return 0;
}

The code works on my MSVC compiler.