foo.cc: In function 'int main()':
foo.cc:8:15: error: 'f' was not declared in this scope
    8 |         cout<<f(n);
      |               ^
foo.cc: In function 'int f(int)':
foo.cc:13:15: error: lvalue required as left operand of assignment
   13 |         if(n=1||n=2)
      |              ~^~~
foo.cc:17:1: warning: control reaches end of non-void function [-Wreturn-type]
   17 | }
      | ^

[Hydro](https://hydro.ac)提供评测服务