// g++ -std=c++11
#include <iostream>

// in C++ 11 a constexpr function must be a single return statement
constexpr int fibonacci(int n) {
  return (n <= 1) ? n : fibonacci(n - 1) + fibonacci(n - 2);
}

int main() {
  constexpr int r = fibonacci(40);
  std::cout << r << std::endl;
}