/in/foo.cc: In function 'int main()':
/in/foo.cc:10:2: error: expected ';' before 'for'
  for(i=4;i<=n-1;i++)
  ^~~
/in/foo.cc:10:11: warning: statement has no effect [-Wunused-value]
  for(i=4;i<=n-1;i++)
          ~^~~~~
/in/foo.cc:10:20: error: expected ';' before ')' token
  for(i=4;i<=n-1;i++)
                    ^
/in/foo.cc:17:8: error: 'f4' was not declared in this scope
  cout<<f4<<endl;
        ^~