program ping;
  type
    arry=record
      s,next:longint;
    end;
    erry=record
      y,v,next:longint;
    end;
  var
    i,j,n,m,t,ans,te,tn,k,min,x,y,v,c,s,oo:longint;
    a:array[1..10000] of arry;
    e:array[1..10000] of erry;
    q:array[1..10000] of longint;
    flag:array[1..10000] of boolean;
    dis:array[1..10000] of longint;
    pre:array[1..10000] of longint;
  procedure insert(x,y,v:longint);
    begin
      inc(t);
      e[t].y:=y;
      e[t].v:=v;
      e[t].next:=a[x].next;
      a[x].next:=t;
      inc(a[x].s);
    end;
  procedure spfa;
    var
      i,j,head,tail,t:longint;
    begin
      fillchar(q,sizeof(q),0);
      fillchar(flag,sizeof(flag),false);
      fillchar(dis,sizeof(dis),$7f);
      oo:=dis[1];
      q[1]:=1;
      flag[1]:=true;
      head:=1;
      tail:=1;
      dis[1]:=0;
      pre[1]:=0;
      while head<=tail do
        begin
          t:=q[head];
          te:=a[t].next;
          for i:=1 to a[t].s do
            begin
              tn:=e[te].y;
              if dis[tn]>dis[t]+e[te].v  then
                begin
                  dis[tn]:=dis[t]+e[te].v;
                  pre[tn]:=t;
                  if not(flag[tn]) then
                    begin
                      flag[tn]:=true;
                      inc(tail);
                      q[tail]:=tn;
                    end;
                end;
              te:=e[te].next;
            end;
          flag[t]:=false;
          inc(head);
        end;
    end;
  procedure find(s:longint);
    var
      i,j:longint;
    begin
      if s=0 then exit
             else inc(ans);
      find(pre[s]);
    end;
  begin
    assign(input,'ping.in');reset(input);
    assign(output,'ping.out');rewrite(output);
    readln(n,m,s);
    for i:=1 to m do
      begin
        readln(x,y,v);
        insert(x+1,y+1,v);
        insert(y+1,x+1,v);
      end;
    spfa;
    s:=s+1;
    find(s);
    if ans>10 then writeln('no')
      else if dis[s]=oo then writeln('no')
         else writeln(dis[s]);
    close(input);close(output);
  end.