WSO 2011 :: Problem D

uses
    SysUtils, Math;

const
    p=10037;
    x:longint=257;

type
    point=record
        x,y,n:int64;
    end;

    ap=array of point;

var
    i,n,k,ii,j,tt:longint;
    a:array[0..2020] of point;
    h:array[0..p] of ap;
    hh,aa:int64;
    pp:point;
    f:boolean;

function hash(s:string):int64;

var
    i:longint;
    c:int64;

begin
result:=0;
c:=1;
for i:=1 to length(s) do begin
        c:=(c*x) mod p;
        inc(result,(ord(s[i])*c) mod p);
        result:=result mod p;
end;
end;

begin
reset(input,'input.txt');
rewrite(output,'output.txt');
read(n);
for i:=1 to n do begin
    read(a[i].x,a[i].y);
    a[i].n:=i;
    tt:=a[i].x+a[i].y+int64(a[i].x)*int64(a[i].y);
    hh:=hash(inttostr(tt));
    tt:=length(h[hh]);
    setlength(h[hh],tt+1);
    h[hh][tt]:=a[i];
end;
for i:=1 to n do
    for j:=1 to n do begin
        if (i=47) and ((j=9) or (j=88) or (j=110)) then begin
            tt:=1;
        end;
        if (a[i].x=a[j].x) or (a[i].y=a[j].y) or
            (abs(a[i].x-a[j].x)<>abs(a[i].y-a[j].y)) then continue else begin
            f:=false;
            pp.x:=a[i].x;
            pp.y:=a[j].y;
            tt:=pp.x+pp.y+pp.x*pp.y;
            hh:=hash(inttostr(tt));
            tt:=length(h[hh]);
            dec(tt);
            for ii:=0 to tt do
                if (pp.x=h[hh][ii].x) and (pp.y=h[hh][ii].y) then begin
                    f:=true;
                    k:=h[hh][ii].n;
                    break;
                end;
            if f then begin
                pp.x:=a[j].x;
                pp.y:=a[i].y;
                tt:=pp.x+pp.y+pp.x*pp.y;
                hh:=hash(inttostr(tt));
                tt:=length(h[hh]);
                dec(tt);
                for ii:=0 to tt do
                    if (pp.x=h[hh][ii].x) and (pp.y=h[hh][ii].y) then begin
                        write(a[i].n,' ',a[j].n,' ',k,' ',h[hh][ii].n);
                        halt(0);
                    end;
            end;
        end;
    end;
write('NO SOLUTION');
end.