program party;
var
  dist,table,map:array [1..1000,0..1000] of longint;
  q:array [0..100000] of longint;
  f:array [1..1000] of boolean;
  max,i,j,n,m,x,a,b,v,head,tail:longint;
procedure spfa;
var now:longint;
begin
  for i:=1 to n do begin
    for j:=1 to n do dist[i,j]:=maxlongint;
    fillchar (f,sizeof(f),0);
    dist[i,i]:=0;f[i]:=true;q[1]:=i;
    head:=1;tail:=1;
    while head<=tail do begin
      now:=q[head];
      for j:=1 to map[now,0] do begin
        if dist[i,map[now,j]]>dist[i,now]+table[now,map[now,j]] then begin
      	  dist[i,map[now,j]]:=dist[i,now]+table[now,map[now,j]];
       	  if f[map[now,j]]=false then begin
            tail:=(tail+1) mod m;
       	    q[tail]:=map[now,j];
	    f[map[now,j]]:=true;
	  end;
	end;
      end;
      f[now]:=false;
      head:=(head+1) mod m;
    end;
  end;
end;
begin
  assign (input,'party.in');
  reset (input);
  readln (n,m,x);
  fillchar (map,sizeof(map),0);
  for i:=1 to n do for j:=1 to n do table[i,j]:=maxlongint;
  for i:=1 to m do begin
    readln (a,b,v);
	if v<table[a,b] then table[a,b]:=v;
  end;
  for i:=1 to n do for j:=1 to n do if table[i,j]<>maxlongint then begin
    inc(map[i,0]);
	map[i,map[i,0]]:=j;
  end;
  close (input);
  assign (output,'party.out');
  rewrite (output);
  fillchar (q,sizeof(q),0);
  spfa;
  max:=0;
  for i:=1 to n do if dist[i,x]+dist[x,i]>max then max:=dist[i,x]+dist[x,i];
  writeln (max);
  close (output);
end.