コンパイルできません。原因を教えてください。
This is pTeX, Version p3.0.1, based on TeX, Version 3.14159 (SJIS) (Web2C 7.3.7)

(./center99.tex
pLaTeX2e <2001/09/04>+0 (based on LaTeX2e <2001/06/01> patch level 0)
(c:/usr/local/share/texmf/ptex/platex/base/jarticle.cls
Document Class: jarticle 2001/10/04 v1.3 Standard pLaTeX class
(c:/usr/local/share/texmf/tex/latex/base/fleqn.clo)
(c:/usr/local/share/texmf/ptex/platex/base/jsize10.clo))
(c:/usr/local/share/texmf/tex/latex/amslatex/amsmath.sty
For additional information on amsmath, use the `?' option.
(c:/usr/local/share/texmf/tex/latex/amslatex/amstext.sty
(c:/usr/local/share/texmf/tex/latex/amslatex/amsgen.sty))
(c:/usr/local/share/texmf/tex/latex/amslatex/amsbsy.sty)
(c:/usr/local/share/texmf/tex/latex/amslatex/amsopn.sty))
(c:/usr/local/share/texmf/tex/latex/amsfonts/amssymb.sty
(c:/usr/local/share/texmf/tex/latex/amsfonts/amsfonts.sty))
(c:/usr/local/share/texmf/tex/latex/tools/enumerate.sty) (./emath.sty
(./emath2e.sty (./emathC.sty (c:/usr/local/share/texmf/tex/latex/tools/calc.sty
)) (./emathE.sty (c:/usr/local/share/texmf/tex/latex/graphics/keyval.sty)
(c:/usr/local/share/texmf/tex/latex/base/ifthen.sty) (./emathMw.sty
(./emathLb.sty)) (./emathK.sty)))) (./hako.sty
(c:/usr/local/share/texmf/tex/latex/tools/verbatim.sty)) (./center99.aux)
(c:/usr/local/share/texmf/tex/latex/amsfonts/umsa.fd)
(c:/usr/local/share/texmf/tex/latex/amsfonts/umsb.fd) (./center99.toc) [1]
(./1a1-1.tex) (./1a1-2.tex) (./1a2-1-1.tex [2]) (./1a2-1-2.tex
(c:/usr/local/share/texmf/tex/latex/base/omscmr.fd)) (./1a2-2.tex) (./1a3.tex
[3]) (./1a4.tex) [4] (./1a5.tex

! LaTeX Error: Environment nidan undefined.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.33 \begin{nidan}
                  {12zw}{\leavevmode\par\vspace{12\baselineskip}
?

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