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