/in/foo.cc: In member function 'void MaxHeap::backspace()':
/in/foo.cc:65:13: warning: unused variable 'now' [-Wunused-variable]
   long long now=a[cnt].pos;
             ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:101:40: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long long int' [-Wformat=]
   else printf("%d\n",a.a[a.heap[1]].val);
                                        ^