foo.cc: In function ‘void Cut(std::vector<double>&, int&)’:
foo.cc:85:26: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<double>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   85 |   for (int i = 0; i + id < a.size(); ++i) {
      |                   ~~~~~~~^~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:113:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<double>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
  113 |     for (int i = 0; i < G.size(); ++i) {
      |                     ~~^~~~~~~~~~