The well-known verbal arithmetic problem
S E N D + M O R E ----------- M O N E Y
explains (or at least it did the first time I knew about it) the story of a student who send a telegram to his father, asking for more money, and asks to fill in each letter with a different digit in order to figure out how much the student was asking for. What's not so broadly known is the answer his father gave:
S P E N D - L E S S ----------- M O N E Y
Even though, the father was not as good as the son with verbal arithmetics and by mistake made an impossible one.
Could you prove that the rest he proposed is impossible?
Of course, feel free to solve the first verbal arithmetic (which can be solved indeed), but the real question is about the impossibility to solve the second one.
Note: The first verbal arithmetic problem is only provided for flavour, and the same letter does not necessarily represent the same number between both equations.