!7

p {
  assertEquals("0", calc("0"));
  assertEquals("1", calc("1"));
  assertEquals("1", calc("1!"));
  assertEquals("1", calc("0!"));
  assertEquals("1", calc("!0"));
  assertEquals("0", calc("!1"));
  assertEquals("0", calc("!0!"));
  assertEquals("1", calc("!!0!"));
  assertEquals("0", calc("!!0"));
  assertEquals("1", calc("!!!0"));
  assertEquals("1", calc("0!!"));
  assertEquals("1", calc("1!!"));
  assertEquals("0", calc("!0!!"));
  assertEquals("0", calc("!0!!!"));
  assertEquals("0", calc("!0!!!!"));
}

sS calc(S s) {
  ret repeatMultiReplace3(s, "0!", "1", "1!", "1", "!0", "1", "!1", "0");
}