foo.cc: In member function 'void tree::add(int, int, int, ll)':
foo.cc:61:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
         if (l<=m) add(p<<1,l,r,c);if (r>m) add(p<<1|1,l,r,c);
         ^~
foo.cc:61:35: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
         if (l<=m) add(p<<1,l,r,c);if (r>m) add(p<<1|1,l,r,c);
                                   ^~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。