Task

You are standing at a magical well. It has two positive integers written on it: a and b. Each time you cast a magic marble into the well, it gives you a * b dollars and then both a and b increase by 1. You have n magic marbles. How much money will you make?

Example

For a = 1, b = 2 and n = 2, the output should be 8

You will cast your first marble and get $2, after which the numbers will become 2 and 3. When you cast your second marble, the well will give you $6. Overall, you'll make $8. So, the output is 8.

Input/Output

• [input] integer a

  Constraints: 1 ≤ a ≤ 2000

• [input] integer b

  Constraints: 1 ≤ b ≤ 2000

• [input] integer n

  The number of magic marbles in your possession, a non-negative integer.

  Constraints: 0 ≤ n ≤ 5

• [output] an integer