foo.cc: In function 'int main()':
foo.cc:7:2: error: 'cin' was not declared in this scope
  cin >>a;
  ^~~
foo.cc:7:2: note: suggested alternative: 'main'
  cin >>a;
  ^~~
  main
foo.cc:8:2: error: 'cout' was not declared in this scope
  cout <<a*a;
  ^~~~

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