const
  oo=maxlongint div 2;

var
  n,m,en,i,j,x,y,z:longint;
  d,q:array[0..100000]of longint;
  v:array[0..100000]of boolean;
  g:array[0..1000,0..1000]of longint;

procedure spfa;
var
  h,t,x,i:longint;
begin
  h:=1;
  t:=1;
  for i:=0 to n-1 do
  begin
    v[i]:=false;
    d[i]:=oo;
  end;
  d[0]:=0;
  q[1]:=0;
  v[0]:=true;
  repeat
    x:=q[h];
    for i:=0 to n-1 do
    if d[x]+g[x,i]<d[i] then
    begin
      d[i]:=d[x]+g[x,i];
      if not v[i] then
      begin
        v[i]:=true;
        inc(t);
        q[t]:=i;
      end;
    end;
    v[x]:=false;
    inc(h);
  until h>t;
end;

begin
  assign(input,'ping.in'); reset(input);
  assign(output,'ping.out'); rewrite(output);
  readln(n,m,en);
  for i:=0 to n do
   for j:=0 to n do
   g[i,j]:=oo;
  for i:=1 to m do
  begin
    readln(x,y,z);
    g[x,y]:=z;
    g[y,x]:=z;
  end;

  spfa;
  if d[en]=oo then writeln('no')
  else writeln(d[en]);
  close(input);
  close(output);
end.