155528

When I was solving the problem, I realised that all consecutive numbers add up to an odd number, E.G 7+8=15 so they could go next to each other. I also knew that an odd number added to another odd number equals an even number and the same is with an even number added to another one. So when I put the first number in the box I knew that the next one needed to be either the number before that one or the one after or any thing which added up to an odd number so I carried on doing that until I got to the last number (the middle one) and then I checked that all the numbers were correct before pressing the "check button" and starting over again.