SUBROUTINE Metropolis(x,delta,naccept)
      IMPLICIT NONE
      REAL*8 w, xtrial, x, delta
      REAL rnd
      INTEGER naccept
      xtrial = x + delta*(2*rnd(0) - 1)
      w = p(xtrial)/p(x)
      IF(rnd(0) .LE. w) THEN
         x = xtrial
         naccept = naccept + 1              ! number of acceptances
      END IF
      END