જો  \(\rm \frac{1}{x}+\frac{1}{y}+\frac{1}{z}=1\), તો \(\rm \left(\frac{1}{z-1}\right)\left(\frac{1}{x}+\frac{1}{y}\right)+ \left(\frac{1}{y-1}\right)\left(\frac{1}{x}+\frac{1}{z}\right)+ \left(\frac{1}{x-1}\right)\left(\frac{1}{y}+\frac{1}{z}\right)=? \)