The USB law.

When you try to plug in a USB-A connector, there’s a 70% probability it won’t go in. Mathematically it should be 50%, but I don’t believe that.

You switch it around, and there’s a 30% probability it won’t go in. This is not something they taught at school.

You switch it around the third time, and there’s a 5% chance it still won’t go in. Your mind begins to melt down, you switch and insert repeatedly until it finally works sooner or later.