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