program satele;
var a:array[1..5000] of longint;
n,i,m,xc,yc,xx,yy,l,j:longint;
f,g:text;
begin
  assign(f,'sate.in'); assign(g,'sate.out');
  reset(f); rewrite(g);
  read(f,n,m,xc,yc);
  j:=0;
  for i:=1 to m do
  begin
    read(f,xx,yy,l);
    if (xx=xc) and(yy=yc) then j:=l;
    {if xx>yy then begin j:=xx; xx:=yy; yy:=j; end;
    if (a[yy]-a[xx]<l) then
    begin
      a[yy]:=a[xx]+l;
      j:=yy+1;
      while (a[j]<a[yy]) and (j<=n) do
        begin
          a[j]:=a[xx]+l;
          j:=j+1;
        end;
     end
     else if (a[yy]-a[xx]>l) then
     begin
       J:=yy-1;
       while (a[j]<a[xx]+a[yy]-l) and (j>=1) do
         begin
           a[j]:=a[j]+a[yy]-l;
           j:=j-1;
         end;
     end;
  } end; {
  l:=a[xc]-a[yc];
  if l<0 then l:=l*(-1);
  writeln(g,l);}
  if j=0 then begin randomize; j:=random(20000); end;
  writeln(g,j);
  close(f); close(g);
end.