foo.cc: In function 'int main()':
foo.cc:19:3: error: 'a' was not declared in this scope
   19 |   a=n/100;
      |   ^
foo.cc:20:3: error: 'b' was not declared in this scope
   20 |   b=n/10%10;
      |   ^
foo.cc:21:3: error: 'c' was not declared in this scope
   21 |   c=n%10;
      |   ^
foo.cc:22:3: error: 'd' was not declared in this scope
   22 |   d=b+c;
      |   ^

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