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