URAL/1097

来自"NOCOW"

const 
 maxm=100; 
var 
 imp,size,x,y:array[0..maxm]of integer; 
 l,a,m,i,u,v,w:integer; 
function ok:boolean; 
var 
 i,j,k,p,q:integer; 
begin 
 for i:=0 to m do 
  if imp[i]>w then 
   for j:=0 to m do 
    if imp[j]>w then
     begin 
      p:=x[i]+size[i];if p+a>l then continue; 
      q:=y[j]+size[j];if q+a>l then continue; 
      ok:=true; 
      for k:=1 to m do 
       if (imp[k]>w) and (p<x[k]+size[k])
       and (x[k]<=p+a) and (q<y[k]+size[k]) and (y[k]<=q+a) then
        begin 
         ok:=false; 
         break; 
        end; 
      if ok then exit; 
     end; 
end; 
begin 
 read(l,a,m);
 a:=a-1; 
 for i:=1 to m do 
  read(imp[i],size[i],x[i],y[i]); 
  imp[0]:=255;size[0]:=1;x[0]:=0;y[0]:=0; 
  u:=1;v:=101; 
 repeat 
  w:=(u+v) shr 1; 
  if ok then v:=w 
  else u:=w+1; 
 until u=v; 
 if u>100 then writeln('IMPOSSIBLE') 
 else writeln(u); 
end.
 
by----wh硕