foo.cc: In function 'int main()':
foo.cc:7:11: error: 'cin' was not declared in this scope
    7 |  float a; cin>>a;
      |           ^~~
foo.cc:4:1: note: 'std::cin' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
    3 | #include<cmath>
  +++ |+#include <iostream>
    4 | using namespace std;
foo.cc:17:2: error: 'cout' was not declared in this scope
   17 |  cout<<fixed<<setprecision(4)<<d;
      |  ^~~~
foo.cc:17:2: note: 'std::cout' is defined in header '<iostream>'; did you forget to '#include <iostream>'?

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