Arithmetic sequence game

The next three numbers should form the correct sequence of arithmetic operations with the use, between the first two numbers (the third number is the result), one of the four arithmetic operations: +, -,:, or x. Number of starting at the beginning level, is always drawn. At any time you can go to the next level by clicking on "Level +", but then you lose points (20 for each number remaining in the game). Warning! One mistake ends the game! R - restart game, www - submit score.