浮点型特判都注意了啊、、、麻了

#include<bits/stdc++.h>
using namespace std;
const double pie=3.1415926535;
int n;
double ans,x[108],y[108];;
double f(int x,int y,int xx,int yy) {
	return sqrt((x-xx)*(x-xx)+(y-yy)*(y-yy));
}

double r;
int main() {
	cin>>n>>r;
	cin>>x[1]>>y[1];
	for(int i=2; i<=n; i++) {
		cin>>x[i]>>y[i];
		ans+=(f(x[i],y[i],x[i-1],y[i-1]));

	}
	ans+=f(x[1],y[1],x[n],y[n]);
	printf("%.2f",(ans+pie*r*2));
	return 0;
}