For each natural number k, let Ck denote the circle with radius k centimeters and center at the origin. On the circle Ck, a particle moves k centimeters in the counterclockwise direction. After completing its motion on Ck the particle moves to Ck + 1 in the radial direction. The motion of the particle continues in this manner. The particle starts at ( 1, 0 ). If the particle crosses the positive direction of the X–axis for the first time on the circle Cn then n = . . . . .