foo.cc: In function 'int main()':
foo.cc:6:2: error: expected initializer before 'cin'
  cin>>n;
  ^~~
foo.cc:7:14: error: 'n' was not declared in this scope
  cout<<pow(2,n)<<endl;
              ^
foo.cc:7:14: note: suggested alternative: 'yn'
  cout<<pow(2,n)<<endl;
              ^
              yn

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