I have problems with this problem somebody can help me?

the problem is in www.sppcontest.org/2003/P8_Vans.pdf

Other favor can you write me to my email

samdsmx@hotmail.com

Hello!

Here is the formula: b[n] = 2 * b[n - 1] + 2 * b[n - 2] - 2 * b[n - 3] + b[n - 4]. This is for unique roads, here we should multiply by 2 because the direction matters.