#include <math.h>
main()
{
    int N,R,i;
    double w[100][2],l;
    double zl=0;
    double hypot(double x,double y);
    double fabs(double num);
    scanf("%d%d",&N,&R);
    for(i=0;i<N;i++)
    scanf("%f%f",&w[i][0],&w[i][1]);
    for(i=0;i<N-1;i++)
    {
        l=hypot(fabs(w[i][0]-w[i+1][0]),fabs(w[i][1]-w[i+1][1]))；
        zl+=l;
    }
    zl+=2*R*3.14159;
    printf("%.2f",zl);
    getch();
}

"l=hypot(fabs(w[i][0]-w[i+1][0]),fabs(w[i][1]-w[i+1][1]))；"编译器说该语句有问题，我查不出，各位高手请伸伸手，我感激不尽！

"double hypot (double x,double y)"已知直角三角形两个直角边长度，求斜边长度