foo.cc: In function 'int main()':
foo.cc:87:15: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
   87 |  PolyList  L1("L1.txt");  L1.Output();
      |               ^~~~~~~~
foo.cc:88:15: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
   88 |  PolyList  L2("L2.txt");  L2.Output();
      |               ^~~~~~~~

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