#include
#define delta 1e-5
int main()
{
double x,y1=2.0,y2,s=0;
for(x=delta;x<=2.0;x+=delta)
y2=sqrt(4-x*x);
s+=(y1+y2)*delta/2.0;
y1=y2;
}
printf("%lf\n",s);
getch();
return 0;
