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My program:

Program t1124;

Var M,N,i,j,k,a  :integer;
    c            :array[1..500]of integer;

begin
a:=0;
fillchar(c,sizeof(c),0);
read(m,n);
for i:=1 to m do
 for j:=1 to n do begin
  read(k);
  if k<>i then begin
   a:=a+1;
   c[i]:=c[i]+1;
  end;
 end;
j:=0;
for i:=1 to m do
 if c[i] mod 2=1 then
  j:=j+1;
if j>0 then a:=a+(j div 2)-1;
writeln(a);
end.

It get WA.
The wrong test:
4
1 2 2
2 1 1
3 4 4
4 3 3
Rigth answer:9
My program's answer:8.

How i can find in program code a such kind of tests?