/*This Code is Submitted by billforum for Problem 2183 at 2012-02-20 15:36:33*/#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           using namespace std;int main(){ int n; double x0,y0,x1,y1,x2,y2; double ans,v; while(scanf("%d",&n)!=EOF) { if(n<3) break; ans=0; scanf("%lf%lf%lf%lf",&x0,&y0,&x1,&y1); for(int i=1;i<=n-2;i++) { scanf("%lf%lf",&x2,&y2); ans+=(x0*y1+x1*y2+x2*y0-y0*x1-y1*x2-y2*x0); x1=x2; y1=y2; } if(ans<0) ans=-ans; scanf("%lf",&v); printf("BAR LENGTH: %.2lf\n",2*v/ans); } return 0;}