Piggy Banks

Taeseok has two piggy banks. Initially, each piggy bank contains 1 won. Each day, he chooses exactly one piggy bank and adds 1 won to it. He stops saving when both piggy banks contain N won.

For a state where the first piggy bank contains a won and the second contains b won, write a followed by b to form one integer. If that integer is prime, call the state a good state. The initial state (1, 1), which forms 11, is not counted.

Taeseok may choose the saving order freely. Among all possible orders, find the maximum possible number of good states.

The first line contains an integer N. (1 <= N <= 999)

Print the maximum possible number of good states.