This is my source code:

#include <iostream>
#include <math.h>

using namespace std;


int main(){
    int N;
    double R, ans=0.0, x1,y1,xt,yt,x,y;
    cin >> N >> R;
    cin >> x1 >> y1;
    xt=x1; yt=y1;
    for (int i=1; i<N; i++){
        cin >> x >> y;
        ans+=sqrt((x-xt)*(x-xt)+(y-yt)*(y-yt));
        xt=x; yt=y;
    }
    ans+=sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
    ans+=2*acos(-1.0)*R;
    cout << floor(ans*100)/100 << endl;
    return 0;
}
P.S. cout << setprecision(2) << ans << endl; isn't Ъ way.

I think You Just be careful when N = 1