//int a,b,c,m,s;{for(;cin>>c;a=b,b=c)m+=m<2|b+b==a+c?b>0:2-m,s+=s<m;wt(s);}
//int@N,@A[N],d,m,s=1;s+=s<(m=d-(d=A[0..N-2]-A[1..])?2:m+1);wt(s);
int@N,@A[N],m,s=1;s+=s<(m=A[-1..N-3]-2*A[0..]+A[1..]?2:m+1);wt(s);