# frozen_string_literal: true

X, Y = gets.chomp.split.map(&:to_i)
_ = gets.to_i
AS = gets.chomp.split.map(&:to_i)

milestones = []
AS[0..-2].each { |a| milestones << (milestones[-1] || 0) + a }

deadlines = [AS[0]]
AS[1..-1].each { |a| deadlines << deadlines[-1] + a }
deadlines.shift

puts(milestones.zip(deadlines).all? { |m, d| m * Y <= X * d } ? 'YES' : 'NO')