Let $\mathrm{A}\left(0,1\right),\mathrm{B}\left(1,1\right),\mathrm{C}\left(1,-1\right),\mathrm{D}\left(-1,0\right)$ be four points. If P is any other point, then $\mathrm{PA}+\mathrm{PB}+\mathrm{PC}+\mathrm{PD}\ge \mathrm{d},$ when $\left[\mathrm{d}\right]$ is ___, where [.] represents greatest integer.