)</span>
<span class="special">{</span>
    <span class="special">...</span>
<span class="special">}</span>

<span class="keyword">int</span> <span class="identifier">system_length</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
<span class="identifier">rk4</span><span class="special">(</span> <span class="identifier">x</span> <span class="special">,</span> <span class="identifier">system_length</span> <span class="special">,</span> <span class="identifier">