foo.cc: In function 'int main()':
foo.cc:9:17: error: 'cin' was not declared in this scope
    9 |                 cin>>a>>b;
      |                 ^~~
foo.cc:15:9: error: 'cout' was not declared in this scope
   15 |         cout<<weekday<<endl;
      |         ^~~~
foo.cc:15:24: error: 'endl' was not declared in this scope
   15 |         cout<<weekday<<endl;
      |                        ^~~~

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