program ping;
const
  maxn=1100;
  maxm=1001000;
type
  node=record
    v,w,next:longint;
  end;
var
  dist,list,q:array[0..maxn] of longint;
  map:array[0..maxm] of node;
  b,bb:array[0..maxn] of boolean;
  n,m,i,j,u,v,r1,r2,r3,h,t,e:longint;
  
procedure addedge(i,j,w:longint);
begin
  inc(e);
  map[e].v:=j;
  map[e].w:=w;
  map[e].next:=list[i];
  list[i]:=e;
  inc(e);
  map[e].v:=i;
  map[e].w:=w;
  map[e].next:=list[j];
  list[j]:=e;
end;
  
begin
  assign(input,'ping.in');
  reset(input);
  assign(output,'ping.out');
  rewrite(output);
  
  readln(n,m,v);
  if v=0 then
  begin
    writeln(0);
    close(input);
    close(output);
    halt;
  end;
  e:=0;
  fillchar(list,sizeof(list),0);
  for i:=1 to m do
  begin
    readln(r1,r2,r3);
    addedge(r1,r2,r3);
  end;
  
  fillchar(dist,sizeof(dist),0);
  fillchar(bb,sizeof(bb),false);
  fillchar(b,sizeof(b),false);
  b[0]:=true;
  bb[0]:=true;
  q[1]:=0;
  h:=0;
  t:=1;
  while h<>t do
  begin
    h:=(h+1) mod n;
    i:=q[h];
    u:=list[i];
    while u<>0 do
    begin
      j:=map[u].v;
      if (not bb[j]) or (dist[i]+map[u].w<dist[j]) then
      begin
        dist[j]:=dist[i]+map[u].w;
        bb[j]:=true;
        if not b[j] then
        begin
          b[j]:=true;
          t:=(t+1) mod n;
          q[t]:=j;
        end;
      end;
      u:=map[u].next;
    end;
    b[i]:=false;
  end;
  
  if dist[v]>0 
    then writeln(dist[v])
    else writeln('no');
  close(input);
  close(output);
end.