foo.cc:6:1: error: expected initializer before 'int'
    6 | int main()
      | ^~~
foo.cc: In function 'int f(int)':
foo.cc:15:15: error: lvalue required as left operand of assignment
   15 |         if(n=1||n=2)
      |              ~^~~
foo.cc:19:1: warning: control reaches end of non-void function [-Wreturn-type]
   19 | }
      | ^

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