The current in an enhancement mode NMOS transistor biased in saturation mode was measured to be $1\: mA$ at a drain-source voltage of $5\: V.$ When the drain-source voltage was increased to $6\: V$ while keeping gate-source voltage same, the drain current increased to $1.02\: mA.$ Assume that drain to source saturation voltage is much smaller than the applied drain-source voltage. The channel length modulation parameter $\lambda\:(\text{in}\: V^{-1})$ is _______.