#include <cassert>
#include <iostream>
#include <ostream>
// requires C++23 to compile
class A {
  long long counter = 0;

public:
  A() : counter{0} {}
  A operator()() {
    A ret = *this;
    ret.counter++;
    return ret;
  }
  // requires C++23 to compile
  A operator[](int _ = 0) {
    A ret = *this;
    ret.counter--;
    return ret;
  }
  // friend std::ostream &operator<<(std::ostream &lhs, A const &rhs) {
  //   lhs << rhs.counter;
  //   return lhs;
  // }
  operator long long() { return counter; }
};

int main(void) {
  A a;
  assert(a == 0);
  assert(a[] == -1);
  assert(a[]() == 0);
  assert(a[]()() == 1);
  for (long long j = 1; j < 100; j++) {
    A a2;
    A a3;
    for (long long k = 0; k < j; k++) {
      assert(a2 == k);
      assert(a3 == -k);
      a2 = a2();
      a3 = a3[];
    }
    assert(a2 == j);
    assert(a3 == -j);
  }
  int i = a;
  assert(i == 0);
  i = a()()()()()()()()()()()();
  assert(i == 12);
  i = a()()()()()()()()()()();
  assert(i == 11);
  i = a()()()()()()()()()()()[];
  assert(i == 10);
  i = a()()()()()()()()()();
  assert(i == 10);
  i = a()()()()()()()()()()[];
  assert(i == 9);
  i = a()()()()()()()()()()[][];
  assert(i == 8);
  i = a()()()()()()()()();
  assert(i == 9);
  i = a()()()()()()()()()[];
  assert(i == 8);
  i = a()()()()()()()()()[][];
  assert(i == 7);
  i = a()()()()()()()()()[][][];
  assert(i == 6);
  i = a()()()()()()()();
  assert(i == 8);
  i = a()()()()()()()()[];
  assert(i == 7);
  i = a()()()()()()()()[][];
  assert(i == 6);
  i = a()()()()()()()()[][][];
  assert(i == 5);
  i = a()()()()()()()()[][][][];
  assert(i == 4);
  i = a()()()()()()();
  assert(i == 7);
  i = a()()()()()()()[];
  assert(i == 6);
  i = a()()()()()()()[][];
  assert(i == 5);
  i = a()()()()()()()[][][];
  assert(i == 4);
  i = a()()()()()()()[][][][];
  assert(i == 3);
  i = a()()()()()()()[][][][][];
  assert(i == 2);
  i = a()()()()()();
  assert(i == 6);
  i = a()()()()()()[];
  assert(i == 5);
  i = a()()()()()()[][];
  assert(i == 4);
  i = a()()()()()()[][][];
  assert(i == 3);
  i = a()()()()()()[][][][];
  assert(i == 2);
  i = a()()()()()()[][][][][];
  assert(i == 1);
  i = a()()()()()()[][][][][][];
  assert(i == 0);
  i = a()()()()();
  assert(i == 5);
  i = a()()()()()[];
  assert(i == 4);
  i = a()()()()()[][];
  assert(i == 3);
  i = a()()()()()[][][];
  assert(i == 2);
  i = a()()()()()[][][][];
  assert(i == 1);
  i = a()()()()()[][][][][];
  assert(i == 0);
  i = a()()()()()[][][][][][];
  assert(i == -1);
  i = a()()()()()[][][][][][][];
  assert(i == -2);
  i = a()()()();
  assert(i == 4);
  i = a()()()()[];
  assert(i == 3);
  i = a()()()()[][];
  assert(i == 2);
  i = a()()()()[][][];
  assert(i == 1);
  i = a()()()()[][][][];
  assert(i == 0);
  i = a()()()()[][][][][];
  assert(i == -1);
  i = a()()()()[][][][][][];
  assert(i == -2);
  i = a()()()()[][][][][][][];
  assert(i == -3);
  i = a()()()()[][][][][][][][];
  assert(i == -4);
  i = a()()();
  assert(i == 3);
  i = a()()()[];
  assert(i == 2);
  i = a()()()[][];
  assert(i == 1);
  i = a()()()[][][];
  assert(i == 0);
  i = a()()()[][][][];
  assert(i == -1);
  i = a()()()[][][][][];
  assert(i == -2);
  i = a()()()[][][][][][];
  assert(i == -3);
  i = a()()()[][][][][][][];
  assert(i == -4);
  i = a()()()[][][][][][][][];
  assert(i == -5);
  i = a()()()[][][][][][][][][];
  assert(i == -6);
  i = a()();
  assert(i == 2);
  i = a()()[];
  assert(i == 1);
  i = a()()[][];
  assert(i == 0);
  i = a()()[][][];
  assert(i == -1);
  i = a()()[][][][];
  assert(i == -2);
  i = a()()[][][][][];
  assert(i == -3);
  i = a()()[][][][][][];
  assert(i == -4);
  i = a()()[][][][][][][];
  assert(i == -5);
  i = a()()[][][][][][][][];
  assert(i == -6);
  i = a()()[][][][][][][][][];
  assert(i == -7);
  i = a()()[][][][][][][][][][];
  assert(i == -8);
  i = a();
  assert(i == 1);
  i = a()[];
  assert(i == 0);
  i = a()[][];
  assert(i == -1);
  i = a()[][][];
  assert(i == -2);
  i = a()[][][][];
  assert(i == -3);
  i = a()[][][][][];
  assert(i == -4);
  i = a()[][][][][][];
  assert(i == -5);
  i = a()[][][][][][][];
  assert(i == -6);
  i = a()[][][][][][][][];
  assert(i == -7);
  i = a()[][][][][][][][][];
  assert(i == -8);
  i = a()[][][][][][][][][][];
  assert(i == -9);
  i = a()[][][][][][][][][][][];
  assert(i == -10);
  i = a;
  assert(i == 0);
  i = a[];
  assert(i == -1);
  i = a[][];
  assert(i == -2);
  i = a[][][];
  assert(i == -3);
  i = a[][][][];
  assert(i == -4);
  i = a[][][][][];
  assert(i == -5);
  i = a[][][][][][];
  assert(i == -6);
  i = a[][][][][][][];
  assert(i == -7);
  i = a[][][][][][][][];
  assert(i == -8);
  i = a[][][][][][][][][];
  assert(i == -9);
  i = a[][][][][][][][][][];
  assert(i == -10);
  i = a[][][][][][][][][][][];
  assert(i == -11);
  i = a[][][][][][][][][][][][];
  assert(i == -12);
  return 0;
}