foo.cc: In function 'int main()':
foo.cc:20:31: error: 'a' was not declared in this scope
                 cout<<n<<"="<<a<<"+"<<b<<endl;
                               ^
foo.cc:20:39: error: 'b' was not declared in this scope
                 cout<<n<<"="<<a<<"+"<<b<<endl;
                                       ^

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