Let's iterate a bit manually, shall we?
force == 2, distance == 18 => moment == 36
force2 == 2, distance2 == 9 => moment2 == 18
force == 3, distance == 18 => moment == 54
force2 == 3, distance == 9 => moment == 27
force == 4, distance == 18 => moment == 72
force2 == 4, distance == 9 => moment == 36
As you see, the way your code works now moment will always be twice as large as moment2.
So you want to find a moment and moment2 that are equal? Then
you should increment either force or force2:
I know find that moment == 36 will break the loop.
If you don't want that break in there you can increase both force and force2 instead. You then get all multiples of 18 except for 0 and 18 itself (since moment will always be larger than 18).