Var
  a,b,c: array[1..3000] of byte;
  i,j,k,n,m: Longint;

begin
  readln(m,n);
  for i := 1 to n do begin
    for j := 1 to m do begin
      read(a[j]);
    end;
    for j := 1 to m do begin
      c[j] := a[j] + b[j];
    end;
    for j := 1 to m-1 do begin
      if ((c[j] = 1) and (c[j+1] = 2)) or ((c[j] = 2) and (c[j+1] =
1)) then begin
        writeln('No');
        halt;
      end;
    end;
    b := a;
    readln;
  end;
  writeln('Yes');
end.

> Var
>   a,b,c: array[1..3000] of byte;
>   i,j,k,n,m: Longint;
>
> begin
>   readln(m,n);
>   for i := 1 to n do begin
>     for j := 1 to m do begin
>       read(a[j]);
>     end;
>     for j := 1 to m do begin
>       c[j] := a[j] + b[j];
>     end;
>     for j := 1 to m-1 do begin
>       if ((c[j] = 1) and (c[j+1] = 2)) or ((c[j] = 2) and (c[j+1] =
> 1)) then begin
>         writeln('No');
>         halt;
>       end;
>     end;
>     b := a;
>     readln;
>   end;
>   writeln('Yes');
> end.
> I have changed readln or read and got AC.