function overint(n,h,f1)
c   function to calculate the integral of one vectors f1
c      using simpsons rule, assuming f1(0)=f1(n+1)=0
c      assumes f1, f2 tabulated at points r=i*h
        implicit real*8 (a-h,o-z)
        dimension f1(n)
        if (n.lt.4) then
        overint=0
        do i=1,n
        overint=overint+h*f1(i)
        enddo
        return
        endif
        fac=h/3
        overint=4*f1(1)+f1(2)
        do i=4,n,2
        overint=overint+f1(i-2)+4*f1(i-1)+f1(i)
        enddo
        overint=fac*overint
        return
        end