text: // If you have access to libstdc++
  // #include <bits/stdc++.h> in order to include
  // every header from the standard C++ library
  
  // Take into account language extensions of your compiler
  
  // Documentation for Clang:
  // http://clang.llvm.org/docs/LanguageExtensions.html
  
  // Documentation for GCC:
  // https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html
  
  #include <cassert>
  
  int main() {
    unsigned long seven = 7;
    assert(__builtin_popcountl(seven) == 3);
  }
  