Alaska, Brownie, Choupette and Doudou are four somalis : two males (Brownie and Doudou) and two females (Alaska and Choupette). They are currently standing each at the corner of a 10m sided square, each one occupying the corner marked with the initial letter of his/her name. But... ... Alaska is in love with Brownie, Brownie with Choupette, Choupette with Doudou and Doudou with Alaska... ... round we go, it's the lovers' quadrille ! (with a little adaptation, the original quadrille is a square dance for 4 couples) Each somali wants to meet his favorite partner, and is constantly moving towards him or her, until they meet. Our four somalis are all moving at the same constant speed. How much will each of them have walked before they all meet ?

... I'm giving up...