Prime Number

problem

One day, Sosusa, who loves prime numbers, was playing with the pair $(p, q)$, where $p + q$ is a prime number. Suddenly, Sosusa wondered how many of these pairs were prime numbers with $p$ and $q$ both less than or equal to $N$. Find the number on your behalf.

output

Output the number of pairs. Also, output a line break at the end.

Example

Input

3

Output

2

inputFormat

outputFormat

output

Output the number of pairs. Also, output a line break at the end.

Example

Input

3

Output

2

样例

3

2