def f(x, y, intersections)
  # spd1, spd2 = [x, y].map{|v| (v * 1000).quo(3600)}

  intersections.each_cons(2){|a, b|
    # p [a.quo(spd1), b.quo(spd2)]
    # return false if a.quo(spd1) > b.quo(spd2)
    return false if a * y > b * x
  }
  true
end

X, Y = gets.split.take(2).map(&:to_i)
N = gets.to_i
A = gets.split.take(N).map(&:to_i)

puts f(X, Y, A) ? :YES : :NO