Obviously, their centers (in the section) form equilateral triangle with the side length of 1 cm.


So, add 1 + 1 + 1 = 3 centimeters for linear elements first. 

Then add to it three times the length of the arc of the circle of the radius 0.5 cm and the central angle of 120 degrees.


So, the final answer is   =  centimeters.