code: function findPeriod() {
      let bestSoFar = 1;
  
      for (let attempts = 0; attempts < 2 * numOutBits; attempts += 1) {
        // NOTE: Here we take advantage of the fact that, for Shor's algorithm,
        // we know that f(x) = f(x+i) ONLY when i is an integer multiple of the rank r.
        if (f(bestSoFar) === f0) {
          dbg(`The period of ${a}^x mod ${n} is ${bestSoFar}`);
          return bestSoFar;
        }
  
        dbg('Starting quantum computation ...');
        const sample = determineFrequency(f);
        dbg('Done quantum computation, result', { sample });
  
        // Each "sample" has a high probability of being approximately equal to some
        // integer multiple of (inputRange/r) rounded to the nearest integer.
        // So we use a continued fraction function to find r (or a divisor of r).
        const continuedFraction = qubitsMath.continuedFraction(
          sample / inputRange,
          accuracyRequiredForContinuedFraction,
        );
        // The denominator is a "candidate" for being r or a divisor of r (hence we need to find
        // the least common multiple of several of these).
        const candidateDivisor = continuedFraction.denominator;
        dbg('Candidate divisor of r: ', { candidateDivisor });
  
        // Reduce the chances of getting the wrong answer by ignoring obviously wrong results!
        if (candidateDivisor > 1 && candidateDivisor <= outputRange) {
          if (f(candidateDivisor) === f0) {
            dbg('This is a multiple of the rank');
            bestSoFar = candidateDivisor;
          } else {
            const lcm = qubitsMath.lcm(candidateDivisor, bestSoFar);
            if (lcm <= outputRange) {
              dbg('This is a good candidate');
              bestSoFar = lcm;
            }
          }
        }
        dbg('Least common multiple so far: ', { bestSoFar, attempts });
      }
      dbg(`Giving up trying to find rank of ${a}`);
      return 'failed';
    }
docs: Determine the period of f (i.e. find r such that f(x) = f(x+r).