这个项目第一次运行的时候打印出房子了，为什么第二次进入的时候出现以下的报错截图？

#include"graphics.h"
#include"genlib.h"
#include<math.h>
#define Len 1.2

void DrawTri(double x, double y, double z);
void DrawRec(double x, double y, double z);

void Main()
{
double w, h, len;
double W, H;

InitGraphics();

W=GetWindowWidth();
H=GetWindowHeight();
w=W/2.0;
h=H*2/3.0;
len=Len/6.0;

//画两个三角形
DrawTri(w-2*Len, h-Len, Len);
DrawTri(w+Len, h-Len, Len);

//画大的正方形
DrawRec(w-Len, h-Len, Len);
DrawRec(w-2*Len, h-Len, Len);
DrawRec(w-Len, h, Len);
DrawRec(w-2*Len, h, Len);
DrawRec(w, h-Len, Len);
DrawRec(w+Len, h-Len, Len);
DrawRec(w, h, Len);
DrawRec(w+Len, h, Len);

//画小的正方形
DrawRec(w-6*len, h-7*len, len);
DrawRec(w-4*len, h-7*len, len);
DrawRec(w-2*len, h-7*len, len);
DrawRec(w+2*len, h-7*len, len);
DrawRec(w+4*len, h-7*len, len);
DrawRec(w+6*len, h-7*len, len);

return;
}

void DrawTri(double x, double y, double z)//以左下角为原点 逆时针
{
MovePen(x,y);
double h=z*sqrt(3)/2;
DrawLine(z, 0);
DrawLine(-z/2, h);
DrawLine(-z/2, -h);
}

void DrawRec(double x, double y, double z)//以左上角为原点 顺时针
{
MovePen(x, y);
DrawLine(z, 0);
DrawLine(0, -z);
DrawLine(-z, 0);
DrawLine(0, z);
}