Arrive at the same time, let the distance from point A to point B be L, and the diameters of three small circles are A, B and C, then the meaning of the problem is that A+B+C=L, so

Pi*(A+B+C)=Pi*L, so Pi*A/2+Pi*B/2+Pi*C/2=Pi*L/2. The semi-perimeters of the three small circles are Pi*A/2, Pi*B/2, and Pi*C/2, respectively.