Neighbor has parked their cars overlapping our driveway
Our neighbor (tenants not owners) have parked totally 3 cars - one in driveway facing garage, 2nd & 3rd one parallel to each other behind the 1st one 
Problem is, i see this 3rd car suddenly (only 2 cars until last week) overlapping my driveway if i can exactly partition a line between our driveways. Honestly if i buy 3 cars, i will first ensure that my cars never touch their driveway or whatever. Regardless of whether it is a major trouble or not, I am not comfortable seeing their car touching my driveway (atleast 10 inches easily).
Just wondering if this is normal & people have come across this and ignore? or should i wait for a few more days & then politely tell them to park in their driveway line?

Problem is, i see this 3rd car suddenly (only 2 cars until last week) overlapping my driveway if i can exactly partition a line between our driveways. Honestly if i buy 3 cars, i will first ensure that my cars never touch their driveway or whatever. Regardless of whether it is a major trouble or not, I am not comfortable seeing their car touching my driveway (atleast 10 inches easily).
Just wondering if this is normal & people have come across this and ignore? or should i wait for a few more days & then politely tell them to park in their driveway line?