Here is my code:
{$r-,s-,q-}

type
 owner=record
        x,y,le:integer;
        import:byte;
       end;
var
 member:array[1..100] of owner;
 n,l,m:integer;

procedure init;
 var
  i:integer;
 begin
  fillchar(member,sizeof(member),0);
  read(n,l);
  read(m);
  for i:=1 to m do
   with member[i] do read(import,le,x,y);
 end;

function touch(x1,x2,y1,y2,x3,x4,y3,y4:integer):boolean;
 begin
  if (((x1>x4) or (x2<x3)) or ((y1>y4) or (y2<y3))) and
     (not ((x1>=x3) and (x2<=x4) and (y1>=y3) and (y2<=y4))) and
     (not ((x3>=x1) and (x4<=x2) and (y3>=y1) and (y4<=y2))) then
   touch:=false
    else
    touch:=true;
 end;

procedure solve;
 var
  i,j,k:integer;
  max,min:byte;
  x1,x2,x3,x4,y1,y2,y3,y4:integer;
  t:boolean;
 begin
  min:=255;
  for i:=1 to n-l+1 do
   for j:=1 to n-l+1 do
    begin
     max:=0;
     x1:=j;x2:=j+l-1;
     y1:=i;y2:=i+l-1;
     for k:=1 to m do
      with member[k] do
      begin
       x3:=x;x4:=x+le-1;
       y3:=y;y4:=y+le-1;
       t:=touch(x1,x2,y1,y2,x3,x4,y3,y4);
       if t and (import>max) then max:=import;
       if max>min then break;
      end;
     if max<min then min:=max;
    end;
  if min<=100 then writeln(min)
   else writeln('IMPOSSIBLE');
 end;

begin
 init;
 solve;
end.