/in/foo.cc:83:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^
/in/foo.cc: In member function 'long long int Segment_Tree::SegmentTree::Build(long long int, long long int, long long int)':
/in/foo.cc:38:17: warning: control reaches end of non-void function [-Wreturn-type]
                 }
                 ^
/in/foo.cc: In member function 'long long int Segment_Tree::SegmentTree::optadd(long long int, long long int, long long int, long long int, long long int, long long int)':
/in/foo.cc:50:17: warning: control reaches end of non-void function [-Wreturn-type]
                 }
                 ^