PROGRAM	near3

c	List waters in interface

	CHARACTER*66	line(4000)
	INTEGER		nres(4000)
	LOGICAL*1	flag(4000)/4000*.FALSE./
	REAL		x(3), z(3)

	WRITE (6, 1000) 'Enter distance criterion:'
	READ (5, 999) crit
999	FORMAT (4f10.4)
	crit = crit*crit

	OPEN (unit=1, file='PCD.pdb.A', status='OLD', readonly)
	DO n = 1,4000
	  READ (1, 1000, end=9) line(n)
1000	  FORMAT (a, f8.3)
	  READ (line(n)(23:26), 1001) nres(n)
1001	  FORMAT (i4)
	  IF (nres(n) .LE. 200) j200 = n
	  IF (nres(n) .LE. 600) j600 = n
	endDO
9	CLOSE (unit=1)
	num = n-1

c	Mark residues in interface

	DO i = 1,j200
	  READ (line(i)(31:54), 1002) x
1002	  FORMAT (3f8.3)
	  DO j = j200+1,j600
	    READ (line(j)(31:54), 1002) z
	    dd = (x(1)-z(1))**2 + (x(2)-z(2))**2 + (x(3)-z(3))**2
	    IF (dd .LE. crit) THEN
	      DO ii = MAX(1,i-30),MIN(j200,i+30)
	        IF (nres(ii) .EQ. nres(i)) flag(ii) = .TRUE.
	      endDO
	      DO jj = MAX(j200+1,j-30),MIN(j600,j+30)
	        IF (nres(jj) .EQ. nres(j)) flag(jj) = .TRUE.
	      endDO
	    endIF
	  endDO
	endDO

c	Mark waters that H bond to residues in interface

	crit = 3.6**2
	DO i = j600+1,num
	  READ (line(i)(31:54), 1002) x
	  DO j = 1,j600
	    IF (flag(j)) THEN
	      READ (line(j)(31:54), 1002) z
	      dd = (x(1)-z(1))**2 + (x(2)-z(2))**2 + (x(3)-z(3))**2
	      IF (dd .LE. crit) flag(i) = .TRUE.
	    endIF
	  endDO
	endDO

c	List residues in interface

	DO i = 1,j600
	  IF (flag(i) .AND. line(i)(14:15) .EQ. 'CA') WRITE (6, 1000) line(i)
	endDO

	DO i = j600+1,num
	  IF (flag(i)) WRITE (6, 1000) line(i)
	endDO

	end