foo.cc: In function 'int main()':
foo.cc:6:5: error: 'cin' was not declared in this scope
    6 |     cin>>a>>b;
      |     ^~~
foo.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
    1 | #include<cstdio>
  +++ |+#include <iostream>
    2 | using namespace std;
foo.cc:9:3: error: 'cout' was not declared in this scope
    9 |   cout<<a+b;
      |   ^~~~
foo.cc:9:3: note: 'std::cout' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
foo.cc:13:3: error: 'cout' was not declared in this scope
   13 |   cout<<"18446744073709551616";
      |   ^~~~
foo.cc:13:3: note: 'std::cout' is defined in header '<iostream>'; did you forget to '#include <iostream>'?

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