const
  fi='stable.inp';
  fo='stable.out';
  maxn=10000;
  maxm=50000;
var
  link,head,ke : array[1..maxm] of longint;
  i,j,n,m,st,ans,s,dau,cuoi,u,v : longint;
  q,bac : array[1..maxn] of longint;
  ok : array[1..maxn] of boolean;
  a : array[1..maxn,1..maxn] of boolean;
procedure push(x : longint);
  begin
    inc(cuoi);
    q[cuoi] := x;
  end;
procedure add(i,u,v : longint);
  begin
    link[i] := head[u];
    head[u] := i;
    ke[i] := v;
  end;
begin
//  assign(input,fi);reset(input);
//  assign(output,fo);rewrite(output);
  read(n,m,s);
  for i := 1 to m do
    begin
      read(u,v);
      if a[u,v] = false then
      add(i,u,v);
      a[u,v] := true;
    end;
  dau := 1; cuoi := 0;
  push(s);
  bac[s] := 1;
  while (dau <= cuoi) do
    begin
      u := q[dau];
      inc(dau);
      i := head[u];
      while i <> 0 do
        begin
          v := ke[i];
          if bac[v] = 0 then
            begin
              if ok[u] then ok[v] := true;
              bac[v] := bac[u] + 1;
              push(v);
            end
            else
          if bac[v] = bac[u] + 1 then
            begin
              ok[v] := true;
            end;
          i := link[i];
        end;
    end;
  for i := 1 to n do
    if ok[i] then inc(ans);
  writeln(ans);
//  close(input);close(output);
end.