foo.cc: In function 'bool OK()':
foo.cc:18:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |  return Next.x >= 0 && Next.x < str.size() && str[Next.x] != ' ' && !f[Next.x][Next.r];
      |                        ~~~~~~~^~~~~~~~~~~~
foo.cc: In function 'int BFS()':
foo.cc:31:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |   if (now.x == str.size() - 1)
      |       ~~~~~~^~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:68:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |   for (int i = 0; i < str.size(); i++)
      |                   ~~^~~~~~~~~~~~

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