Goal: put your kings in c5 and f4.
You have to move opponent from path a3-f8 and c1-h6.
g1-e3 2 kings in one line e7-b4 a1-f6 We started used king on big diagonal b4-a5 e3-c5
Goal: build Petrov's triangle
...a5-d8 f6-c3 d8-h4
The position with kings on c5, f4, c3 is Petrov's triangle.
There are four different triangles of Petrov.
Use rule: "move king from triangle's top to king located on big diagonal"
Let us apply the rule for pos 5:
The top of triangle is f4. The stones should be moved to d2