      ranges <code class="computeroutput"><span class="identifier">rng1</span></code> and <code class="computeroutput"><span class="identifier">rng2</span></code> into a single sorted range by
            copying elements. <code class="computeroutput"><span class="identifier">merge</span></code>
            is stable. The return value is <code class="computeroutput"><span class="identifier">out</span>
            <span class="special">+</span> <span class="identifier">distance</span><span class="special">(<