program sparty;
var
  i,j,k:longint;
  n,m,s:longint;
  a:array[1..1000,1..1000]of longint;
  a1,a2:array[1..1000]of longint;
  f:array[0..100000]of longint;
  o,p,q:longint;
  max:longint;
procedure spfa1;
var
  i:longint;
  head,tail:longint;
begin
  head:=1;
  tail:=1;
  while head<=tail do
  begin
    for i:=1 to n do
      if a1[f[head]]+a[f[head],i]<a1[i] then
      begin
        a1[i]:=a1[f[head]]+a[f[head],i];
        inc(tail);
        f[tail]:=i;
      end;
    inc(head);
  end;
end;
procedure spfa2;
var
  i:longint;
  head,tail:longint;
begin
  head:=1;
  tail:=1;
  while head<=tail do
  begin
    for i:=1 to n do
      if a2[f[head]]+a[i,f[head]]<a2[i] then
      begin
        a2[i]:=a2[f[head]]+a[i,f[head]];
        inc(tail);
        f[tail]:=i;
      end;
    inc(head);
  end;
end;
begin
  assign(input,'party.in');
  reset(input);
  assign(output,'party.out');
  rewrite(output);
  readln(n,m,s);
  for i:=1 to n do
    for j:=1 to n do
      a[i,j]:=236549210;
  for i:=1 to n do
    a[i,i]:=0;
  for i:=1 to m do
  begin
    read(o,p);
    readln(a[o,p]);
  end;
  f[0]:=1;
  f[1]:=s;
  for i:=1 to n do
    a1[i]:=maxint;
  a1[s]:=0;
  spfa1;
  f[1]:=s;
  for i:=1 to n do
    a2[i]:=maxint;
  a2[s]:=0;
  spfa2;

  for i:=1 to n do
    if a1[i]+a2[i]>max then
      max:=a1[i]+a2[i];
  writeln(max);
  close(input);
  close(output);
end.