/in/foo.cc: In member function 'int Solution::solve(std::vector<std::vector<int> >&)':
/in/foo.cc:25:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < intervals.size(); ++i) {
                         ~~^~~~~~~~~~~~~~~~~~
/in/foo.cc:20:14: warning: unused variable 'flag' [-Wunused-variable]
         bool flag = false;
              ^~~~