poj 2812 Extrusion

#include<stdio.h>int main(){double dVertice[20][2],dArea,dVolumn;int iVerticeNum,i;while(scanf("%d",&iVerticeNum) && iVerticeNum!=0){for(i=0;i<iVerticeNum;i++)scanf("%lf%lf",&dVertice[i][0],&dVertice[i][1]);scanf("%lf",&dVolumn);for(i=0,dArea=0.0;i<iVerticeNum;i++)dArea+=dVertice[(i+1)%iVerticeNum][0]*dVertice[i%iVerticeNum][1]-dVertice[(i+1)%iVerticeNum][1]*dVertice[i%iVerticeNum][0];printf("BAR LENGTH: %.2lfn",2.0*dVolumn/dArea);}}