Level shift 0/5V to -10V/+10V

Can anyone show me a simple circuit to shift a 0V/5V square wave (low freq, under 10Hz) to a square wave -10V (when was 0) to +10V (when was +5V). Can it be done with some transistor or do I need an opamp?

Answer

Rather than an op amp, a comparator is a good fit for this. In the following circuit, anything below about 2.5V on the input will give a -10V output, anything above will give +10V. The output of the LM393 is open collector, which makes things simpler than needing a rail to rail op amp.

^{simulate this circuit – Schematic created using CircuitLab}

(I made a mistake in the original with the potential divider values. I've updated the schematic)