foo.cc: In function 'int main()':
foo.cc:6:2: error: 'cin' was not declared in this scope
  cin<<a;
  ^~~
foo.cc:6:2: note: suggested alternative: 'main'
  cin<<a;
  ^~~
  main
foo.cc:10:6: error: 'n' was not declared in this scope
  if (n==7&&b[0]==2&&b[1]==3&&b[2]==4)
      ^
foo.cc:11:3: error: 'cout' was not declared in this scope
   cout<<2;
   ^~~~

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