I can't understand what's wrong with my code
is my algorithm wrong? or what?
my code:

#include <stdio.h>
#include <math.h>
double x[102],y[102];

double dist(int i, int j){
    int d1=abs(x[i]-x[j]),d2=abs(y[i]-y[j]);
    if(d1==0)
        return (d2);
    else if(d2==0)
      return (d1);
    else
      return sqrt(d1*d1 + d2*d2);
}

int main(){
    int i;
    double n,s=0,r,pi=2*acos(0);
  scanf("%Lf %Lf",&n,&r);
  for(i=0;i<n;i++)
      scanf("%Lf %Lf",&x[i],&y[i]);
    for(i=1;i<n;i++)
        s+=dist(i,i-1);
    s+=dist(0,n-1);
    s+=2*pi*r;
    printf("%.2Lf\n",s);
  return 0;
}

if someone can help me I would appreciate very much
thanks!