Let the vectors $\vec{a}, \vec{b}, \vec{c}$, be such that $|\vec{a}|=2,|\vec{b}|=4$ and $|\vec{c}|=4$ and $|\vec{c}|=4$. If the projection of $\vec{b}$ on $\vec{a}$ is equal to the projection of $\vec{c}$ on $\vec{a}$ and $\vec{b}$ is perpendicular to $\vec{c}$, then the value of $|\vec{a}+\vec{b}-\vec{c}|$ is $\_\_\_\_$ .