program ping;
var
  i,j,k,l:longint;
  a:array[0..999,0..999]of longint;
  f:array[1..100000]of longint;
  p:array[0..999]of longint;
  n,m,t:longint;

begin
  assign(input,'ping.in');
  reset(input);
  assign(output,'ping.out');
  rewrite(output);

  readln(n,m,t);
  for i:=0 to n-1 do
    for j:=0 to n-1 do
      a[i,j]:=-1;
  for i:=1 to m do
  begin
    readln(j,k,l);
    a[j,k]:=l;
    a[k,j]:=l;
  end;

  p[0]:=0;
  for i:=1 to n-1 do
    p[i]:=maxlongint;
  f[1]:=0;
  i:=1;
  j:=1;
  while i<=j do
  begin
    for k:=0 to n-1 do
      if a[f[i],k]<>-1 then
      begin
        if p[f[i]]+a[f[i],k]<p[k] then
        begin
          inc(j);
          f[j]:=k;
          p[k]:=a[f[i],k]+p[f[i]];
        end;
      end;
    inc(i);
  end;

  if p[t]<>maxlongint then
    writeln(p[t])
  else
    writeln('no');

  close(input);
  close(output);
end.