foo.cc:4:10: error: expected unqualified-id before ‘;’ token
    4 | string a,;
      |          ^
foo.cc: In function ‘int main()’:
foo.cc:11:25: error: ‘a2’ was not declared in this scope; did you mean ‘a’?
   11 |                 cin>>a>>a2>>a2>>a2;
      |                         ^~
      |                         a