line1 = gets.chomp!
abort 'l1' unless line1 =~ /^\d+$/
n = line1.to_i
abort 'n' unless 3 <= n && n <= 50000

line2 = gets.chomp!
abort 'l2' unless line2 =~ /^\d+(?: \d+)+$/
aa = line2.split(' ').map(&:to_i)
abort 'kk' if aa.each_cons(3).all?{|a,b,c| ((a<b&&b>c)||(a>b&&b<c))&&(a!=c)}
abort 'aa' unless aa.any?{|a| 1 <= a && a <= n}
abort 'aa.size' unless aa.size == n

abort 'break' if gets