Two weights of equal mass m, connected by a spring of stiffness k, which is in an uncompressed state, slide along a smooth board without friction at a speed v0 (figure). At the moment t = 0, the left mass is at a distance L from the vertical wall, in the direction towards which they are both moving. After what time t will the center of mass be in the same position as at the moment t = 0? The impact on the wall is considered instantaneous and absolutely elastic.

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