I guess it was like this: After the invention of natural numbers, one day someone (let us say $A$) was collecting apples. When returning home, he met one of his friends, $B$, who was quite hungry and had

We all are familiar with the basic mathematical operations that can be performed with natural numbers. The addition is the most natural one: We have $x$ elements on one hand, $y$ elements on the other,

The natural numbers are 1, 2, 3, 4, ..., up to infinity. They look simple, but they are not. One of the first interesting things about these numbers is that they confront us in a very natural way with