foo.cc: In function 'int F(int)':
foo.cc:14:7: error: lvalue required as left operand of assignment
   14 |  F(1)=1;
      |       ^
foo.cc:15:7: error: lvalue required as left operand of assignment
   15 |  F(2)=1;
      |       ^
foo.cc:17:19: error: lvalue required as left operand of assignment
   17 |  F(m)=F(m-1)+F(m-2);
      |                   ^

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