Update to a current IDE version (1.8.5 is available). This looks like a bad installation.
You might compile the above if you remove the Serial.begin() call. You don't need it and it's part of that call that makes problems.
Update to a current IDE version (1.8.5 is available). This looks like a bad installation.
You might compile the above if you remove the Serial.begin() call. You don't need it and it's part of that call that makes problems.