x_speed, y_speed = gets.split.map(&:to_i)
count = gets.chomp.to_i
list = gets.split.map(&:to_i)
x_per_second = x_speed * 1000 / 3600
y_per_second = y_speed * 1000 / 3600
flag = true
for i in 0...(count - 1) do
	if list[i + 1].to_f / list[i].to_f < y_speed / x_speed
		break flag = false
	else
		flag = true
	end
end

if flag
	puts "YES"
else
	puts "NO"
end