program Zadacha;

{$APPTYPE CONSOLE}

uses
  SysUtils;
 var i,j,n,m,l,k,s,p,r:integer;
 A:array[1..1000,1..1000] of integer;
 B:array[1..1000] of integer;
 C:array[1..1000] of byte;
 f1,f2:text;
begin
  { TODO -oUser -cConsole Main : Insert code here }
 assign(f1,'penalty.in');
 assign(f2,'penalty.out');
 reset(f1);
 rewrite(f2);
 readln(f1,n,m);
 for i:=1 to n do
 begin
  for j:=1 to n do
  begin
   A[i,j]:=99999;
  end;
 end;
 for i:=1 to m do
 begin
  readln(f1,j,l);
  A[j,l]:=1;
  A[l,j]:=1;
 end;
 readln(f1,p);
 for i:=1 to n-1 do
 begin
  for j:=i+1 to n do
  begin
   for l:=1 to n do
   begin
    if (i<>l) and (j<>l) then
    if (A[i,j]<>99999) and (A[i,l]<>99999) and (A[l,j]<>99999)then
    begin
     A[i,j]:=0;
     A[j,i]:=0;
    end;
   end;
  end;
 end;
 for i:=1 to n do
 begin
  B[i]:=A[1,i];
 end;
 C[1]:=1;
 for l:=1 to n-1 do
 begin
  m:=99998;
  for i:=1 to n do
  begin
   if (C[i]=0) and (m>B[i]) then
   begin
    k:=i;
    m:=B[i];
   end;
  end;
  C[k]:=1;
  for i:=2 to n do
  begin
   if B[i]>B[k]+A[k,i] then
   B[i]:=B[k]+A[k,i];
  end;
 end;
 r:=B[p]*1000;
 writeln(f2,r);
 close(f1);
 close(f2);
end.