subroutine interv (x,n,y,i)
c---find the interval in the motonically increasing table
c---of n elements starting in x(1) in which y is located.
c---i is the index of the lower element of the table.
c------------------------------------------------------------------------
c
      include 'ucom.h'
c
      dimension x(n)
c-----------------------------------------------------------------------
c*
      m=1
      if (n.lt.2) go to 20
      do 10 j=2,n
      if (y.le.x(j)) go to 20
      m=j
  10  continue
  20  continue
      i=m
      return
      end
c++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*