We're assuming arbitrary amounts of time - in which case one can check calculations an arbitrary number of times. (Quick idea: recheck all calculations done so

We're assuming arbitrary amounts of time - in which case one can check calculations an arbitrary number of times. (Quick idea: recheck all calculations done so far at all computation steps that are powers of 2. So recheck everything after the first step, the second step, the fourth step, the eighth step, the sixteenth step, etc.)