require'prime'
m,n,*c=$<.read.split.map &:to_i
d=[-1]*m<<r=0
(0..m.downto(0){|i|c.map{|j|d[i]<0||j>i||d[i-j]=[d[i-j],d[i]+1].max}}).map{|i|r+=i.prime?&&d[i]>0?d[i]:0}
p r+d.max