foo.cc: In function 'int main()':
foo.cc:7:9: error: 'cin' was not declared in this scope
    7 |         cin>>num;
      |         ^~~
foo.cc:3:1: note: 'std::cin' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
    2 | #include<string>
  +++ |+#include <iostream>
    3 | using namespace std;
foo.cc:11:17: error: 'cout' was not declared in this scope
   11 |                 cout<<num[len-1-i];
      |                 ^~~~
foo.cc:11:17: note: 'std::cout' is defined in header '<iostream>'; did you forget to '#include <iostream>'?

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