QBSQUARE PASCAL

uses math;
var    m,n,max:longint;
a,f:array[0..1000,0..1000] of longint;

procedure nhap;
var    i,j:longint;
begin
   readln(m,n);
   for i:=1 to m do
   begin
      for j:=1 to n do read(a[i,j]);
      readln;
   end;
end;

procedure solve;
var    i,j,x,y:longint;
begin   
   max:=0;
   for i:=1 to m do
      for j:=1 to n do
      begin
         x:=i-1;y:=j-1;
         if (a[i,j]=a[x,j]) and (a[i,j]=a[i,y]) and (a[i,j]=a[x,y]) then
            f[i,j]:=min(f[i,y],min(f[x,j],f[x,y]))+1
         else f[i,j]:=1;
         if f[i,j]>max then max:=f[i,j];
      end;
   write(max);
end;

begin
   assign(input, 'qbsquare.inp');reset(input);
   assign(output, 'qbsquare.out');rewrite(output);
   nhap;
   solve;
end.