Let \( C \) be a circle with radius \( \sqrt{10} \) units and centre at the origin. Let the line \( x + y = 2 \) intersects the circle \( C \) at the points \( P \) and \( Q \). Let \( MN \) be a chord of \( C \) of length \( 2 \) unit and slope \( -1 \). Then, a distance (in units) between the chord \( PQ \) and the chord \( MN \) is:
