The problem is this.

The tutorial says this:

"If a fraction can be obtained with k resistors, then it is simple to calculate that we can obtain fractions and with k + 1 resistors. So adding one resistor means performing one operation backwards in Euclidean algorithm. That means that the answer is equal to the number of steps in standard Euclidean algorithm.

At first we thought about the major problem (any two elements can be joined), but had a moment of eureka and got that the given problem unexpectedly naturally can be reduced to GCD. "

I do not understand the tutorial. A little help will be really appreciated.

Thanks!