/in/foo.cc: In member function 'void segment_tree::bulid(int, int, int)':
/in/foo.cc:14:4: error: 'cin' was not declared in this scope
    cin>>sum[x];return;
    ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:64:2: error: 'cin' was not declared in this scope
  cin>>n>>mod;
  ^~~
/in/foo.cc:69:13: error: 'cout' was not declared in this scope
   if(op==3) cout<<seg.query_sum(1,l,r)<<endl;
             ^~~~
/in/foo.cc:69:41: error: 'endl' was not declared in this scope
   if(op==3) cout<<seg.query_sum(1,l,r)<<endl;
                                         ^~~~