SUBROUTINE MIDPNT(FUNC,A,B,S,N)
      IF (N.EQ.1) THEN
        S=(B-A)*FUNC(0.5*(A+B))
        IT=1
      ELSE
        TNM=IT
        DEL=(B-A)/(3.*TNM)
        DDEL=DEL+DEL
        X=A+0.5*DEL
        SUM=0.
        DO 11 J=1,IT
          SUM=SUM+FUNC(X)
          X=X+DDEL
          SUM=SUM+FUNC(X)
          X=X+DEL
11      CONTINUE
        S=(S+(B-A)*SUM/TNM)/3.
        IT=3*IT
      ENDIF
      RETURN
      END