Two runners are running for $1$ hour in the Olympic stadium.
One of them $A$ is faster than the other one $B$.
Runner $A$ completes $50$ rounds in $1$ hour and runner $B$ completes $35$ rounds in $1$ hour.
The runners are switching between them a torch while $A$ is holding the torch at the beginning.
Every time $A$ passes $B$ they are switching the torch between them.
How many rounds the torch completed the stadium in $1$ hour?
I tried to build equations but didn't succeed.