There are more year problems than years. But since I have been pondering on this particular one, I will present it here. You are allowed to use +, -, / and * (plus, minus, division and multiplication) signs and bracketing. These signs you can put between the numbers
to form mathematical expressions. You must put at least one sign between two numbers and – cannot be used as “negative”, thus -1+9+6+3 is not allowed, but 1-9+6+3 is allowed.
The question is: what is the smallest natural number that cannot be expressed in this way?
Hinty example: 1*9-6-3=0 and (1/9)*(6+3)=1, so the answer is greater than 1.