#include <iostream>
#include <string>

using namespace std;

struct reader
{ string value;
  bool used;

  reader()
  { used = false; }

  string read_string()
  { string r;
    if (used)
    { used = false;
      r = value; }
    else
      cin >> r;
    return r; }

  string sneak_peek()
  { string r;
    if (! used)
      cin >> value;
    r = value;
    used = true;
    return r; }

  void clear()
  { used = false; }
};

struct Sexpr
{ char kind;     // 'L' = list link, 'A' = atom
  string atom;
  Sexpr * head, * tail;

  Sexpr(string a)
  { kind = 'A';
    atom = a; }

  Sexpr(Sexpr * h, Sexpr * t)
  { kind = 'L';
    head = h;
    tail = t; }

  void print()
  { if (this == NULL)
    { cout << "( )";
      return; }
    if (kind == 'A')
    { cout << atom;
      return; }
    cout << "( ";
    Sexpr * ptr = this;
    while (ptr != NULL)
    { ptr->head->print();
      cout << " ";
      ptr = ptr->tail; }
    cout << ")"; }
};

/*
int main()
{ Sexpr * F = new Sexpr("3");
  Sexpr * E = new Sexpr(F, NULL);
  Sexpr * D = new Sexpr("2");
  Sexpr * C = new Sexpr(D, E);
  Sexpr * B = new Sexpr("1");
  Sexpr * A = new Sexpr(B, C);
  A->print(); }
*/

Sexpr * read_rest_sexpr(reader & R);

Sexpr * read_sexpr(reader & R)
{ string a = R.read_string();
  if (a == "(")
    return read_rest_sexpr(R);
  if (a == ")")
  { cout << "ERROR unexpected )\n";
    a = "???"; }
  return new Sexpr(a); }

Sexpr * read_rest_sexpr(reader & R)   // read an Sexpression that begins with a (,
                                      // but the ( has already been read
{ string a = R.sneak_peek();
  if (a == ")")
  { R.read_string();
    return NULL; }
  Sexpr * h = read_sexpr(R);
  Sexpr * t = read_rest_sexpr(R);
  return new Sexpr(h, t); }

int str_to_int(string s)
{ int r = 0, n = s.length();
  for (int i = 0; i < n; i += 1)
    r = r * 10 + s[i] - '0';
  return r; }

string int_to_str(int n)
{ string r = "";
  if (n > 9)
    r = r + int_to_str(n / 10);
  return r + (char)('0' + n % 10); }

Sexpr * add(Sexpr * A, Sexpr * B)
{ return new Sexpr(int_to_str(str_to_int(A->atom) + str_to_int(B->atom))); }

Sexpr * mul(Sexpr * A, Sexpr * B)
{ return new Sexpr(int_to_str(str_to_int(A->atom) * str_to_int(B->atom))); }

Sexpr * eval(Sexpr * E)
{ if (E == NULL)
    return NULL;
  if (E->kind == 'A')
    return E;
  Sexpr * h = E->head;
  if (h->kind != 'A')
  { cout << "ERROR " << h->atom << " is not sn operation\n";
    return NULL; }
  if (h->atom == "quote")
    return E->tail->head;
  if (h->atom == "+")
  { Sexpr * ptr = E->tail;
    Sexpr * sum = new Sexpr("0");
    while (ptr != NULL)
    { sum = add(sum, eval(ptr->head));
      ptr = ptr->tail; }
    return sum; }
  if (h->atom == "*")
  { Sexpr * ptr = E->tail;
    Sexpr * sum = new Sexpr("1");
    while (ptr != NULL)
    { sum = mul(sum, eval(ptr->head));
      ptr = ptr->tail; }
    return sum; }
  cout << "can't handle operator " << h->atom << " yet\n";
  return NULL; }

int main()
{ reader R;
  while (true)
  { R.clear();
    cout << "> ";
    Sexpr * x = read_sexpr(R);
    eval(x)->print();
    cout << "\n\n"; } }