2. Watering the Garden
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

There are $$$N$$$ trees in a garden, arranged in a straight line. The distance between adjacent trees is one meter. The distance from the well to the first tree is also one meter. Watering one tree requires one bucket of water.

Vasya waters the trees as follows: he fills two buckets of water at the well, walks to the last two trees to water them, then returns to the well, and the process repeats.

Your task is to find a formula that calculates the total distance Vasya travels. For example, when $$$N=3$$$, your formula should yield a result of 8.

In your formula, you may use only the following elements:

  • the variable $$$N$$$,
  • any integers from -1000 to 1000,
  • parentheses,
  • the binary operators +, -, *, /, and %.

The '/' operator denotes integer division (e.g., 8 / 3 = 2, -8 / 3 = -2). The '%' operator denotes the remainder (e.g., 8 % 5 = 3, -8 % 5 = -3). Multiplication, division, and remainder operations have higher precedence than addition and subtraction. The multiplication symbol cannot be omitted.

When submitting your solution, please select PHP (you don't need to know it, it's just a feature of the system).

Scoring

The correctness of your formula will be verified automatically by substituting various values ​​of $$$N$$$ (ranging from 1 to 1000) into it. Points will be awarded for each correct answer. The maximum possible score is 100.