View Compilation Error

0_0_38975027_8994.cpp: In function 'int main()':
0_0_38975027_8994.cpp:23:27: error: invalid operands of types 'node [1005]' and 'double' to binary 'operator+'
   23 |                 sort(a+1,a+n+1,cmp);ans=0;
      |                          ~^~
      |                          | |
      |                          | double
      |                          node [1005]