H(i+1)-H(i)=H(i)-H(i-1)+2;

denote d(i)=H(i+1)-H(i)

you can get: d(i)=d(i-1)+2;

H(N)-H(1)=(N-1)d(1)+(N-1)(N-2);

H(i)-H(1)=(N-1)d(i)+(i-1)(i-2);

according to the above two equation, denote H(i)=0

you will get:H(N)=(N-i)*((N-1)-H1/(i-1));

the maximun of H(N) is the answer .so strange!

Edited by author 08.03.2009 15:00

Edited by author 08.03.2009 15:00