program zzn;
var
        i,j,n,x,xx,yy,t,m,k,max:longint;
        a:array[1..1000,1..1000]of longint;

procedure init;
begin
        assign(input,'party.in');
        reset(input);
        assign(output,'party.out');
        rewrite(output);
        readln(n,m,x);
        for i:=1 to n do
         for j:=1 to n do if i=j then a[i,j]:=0 else
          a[i,j]:=100000;
        for i:=1 to m do
         begin
             readln(xx,yy,t);
             a[xx,yy]:=t;
         end;
end;
procedure closef;
begin
        close(input);
        close(output);
end;

procedure main;
begin
        for k:=1 to n do
         for i:=1 to n do
           for j:=1 to n do
             begin
                 if a[i,j]>a[i,k]+a[k,j] then
                  a[i,j]:=a[i,k]+a[k,j];
             end;
        max:=-1;
        for i:=1 to n do if i<>x then
         begin
             if max<a[i,x]+a[x,i] then max:=a[i,x]+a[x,i];
         end;
       writeln(max);
end;
begin
        init;
        main;
        closef;
end.