Let \( \vec{a}, \vec{b}, \vec{c} \) be three vectors such that
\[
\vec{a} \times \vec{b} = 2(\vec{a} \times \vec{c}).
\]
If \( |\vec{a}| = 1 \), \( |\vec{b}| = 4 \), \( |\vec{c}| = 2 \), and the angle between \( \vec{b} \) and \( \vec{c} \) is \(60^\circ\), then \( |\vec{a} \cdot \vec{c}| \) is equal to.