/in/foo.cc: In member function 'void SegmentTree::build(ll*)':
/in/foo.cc:103:15: error: 'n' was not declared in this scope
   build(a, 1, n, 1);
               ^
/in/foo.cc: In member function 'void SegmentTree::add(ll, ll, ll)':
/in/foo.cc:107:10: error: 'n' was not declared in this scope
   jia(1, n, 1);
          ^
/in/foo.cc: In member function 'void SegmentTree::set(ll, ll, ll)':
/in/foo.cc:111:10: error: 'n' was not declared in this scope
   gai(1, n, 1);
          ^
/in/foo.cc: In member function 'void SegmentTree::mul(ll, ll, ll)':
/in/foo.cc:115:12: error: 'n' was not declared in this scope
   cheng(1, n, 1);
            ^
/in/foo.cc: In member function 'll SegmentTree::query(ll, ll)':
/in/foo.cc:119:12: error: 'n' was not declared in this scope
   query(1, n, 1);
            ^