answer.code: In function ‘int main()’:
answer.code:66:16: error: ‘cout’ was not declared in this scope
   66 |                cout<<(last=sum)<<'\n';
      |                ^~~~
answer.code:7:1: note: ‘std::cout’ is defined in header ‘<iostream>’; did you forget to ‘#include <iostream>’?
    6 | #include <algorithm>
  +++ |+#include <iostream>
    7 |