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- Project Euler #88: Product-sum numbers

# Project Euler #88: Product-sum numbers

# Project Euler #88: Product-sum numbers

_{This problem is a programming version of Problem 88 from projecteuler.net}

A natural number, , that can be written as the sum and product of a given set of at least two natural numbers, is called a product-sum number: .

For example, .

For a given set of size, , we shall call the smallest with this property a minimal product-sum number. The minimal product-sum numbers for sets of size, are as follows.

Hence for , the sum of all the minimal product-sum numbers is ; note that is only counted once in the sum.

In fact, as the complete set of minimal product-sum numbers for is , the sum is .

What is the sum of all the minimal product-sum numbers for ?

**Input Format**

First and only line contains an integer .

**Constraints**

**Output Format**

Print the required answer.

**Sample Input**

```
12
```

**Sample Output**

```
61
```