c  **************************************************************
       subroutine cal_twist(n,twist)

       implicit double precision(a-h, o-z)
       parameter(maxa=500,pi=3.1415926535d0,pi2=pi*2.d0)
       double precision twist
       integer n
       common/tor_param/ dr,cg,phi0,dlk,phii,subseg
       common/euler/ alpha(maxa),beta(maxa),gama(maxa),phi(maxa)
      

       twist=0.d0
       do i=1,n
        twist=twist+phi(i)
       enddo
       twist=twist/pi2
       return
       end