求fibonacci数列的前40项

void main()
{
	int y1=1,y2=1,y,sum=2;
	for(int i=2;i<4;i++)
	{
		y=y1+y2;
		y1=y2;
		y2=y;
		sum+=y;                   	}
	cout<<"sum="<<sum<<endl;
}