In an electrochemical reaction of lead, at standard temperature, if $\mathrm{E}_{\left(\mathrm{Pb}^{2+} / \mathrm{Pb}\right)}^0=\mathrm{m}$ Volt and $\mathrm{E}_{\left(\mathrm{Pb}^{4+} / \mathrm{Pb}\right)}^0=\mathrm{n}$ Volt, then the value of $\mathrm{E}_{\left(\mathrm{Pb}^{* /} / \mathrm{Pb}^{4+}\right)}^0$ is given by $\mathrm{m}-\mathrm{xn}$. The value of x is $\_\_\_\_$ . (Nearest integer)