if(n<=0||end-start<=0.0)
{ printf("Start is larger than end , or n<=0 in integral!");
exit(1); }
h=(end-start)/n;
al=start+h*0.4226497308;
be=start+h*1.577350269;
sum=(*f)(al)+(*f)(be);
m=n/2-1;
for(i=1;i<=m;i++)
{
al=al+2*h;
be=be+2*h;
sum=sum+(*f)(al)+(*f)(be);