def ascan; gets.split.map(&:to_i); end
def scan; gets.to_i; end

x,y = ascan.map!{|e| Rational(e)}
gets
aa = ascan.map!{|e| Rational(e)}

dist = aa[0]

1.upto(aa.size-1){|i|
    t = aa[i] / y
    k = t * x
    if (k < aa[i-1])
        puts "NO" ; exit(0)
    end
}
puts "YES"