L=5000000
P=[1]*(L+1)
for i in range(2,L+1):
  if P[i]:
    for j in range(i+i,L+1,i):
      P[j]=0

n=int(input())
a=list(map(int,input().split()))
s=0
for v in a:
  s|=1<<v
ans=-1
r=1
t=0
c=[0]*10
for l in range(1,L+1):
  while r+1<=L and t&s==t:
    if t==s:
      ans=max(ans,r-l)
    r+=1
    if P[r]:
      for v in list(map(int,str(r))):
        if c[v]==0:
          t|=1<<v
        c[v]+=1
    if t==s:
      ans=max(ans,r-l)
  if P[l]:
    for v in list(map(int,str(l))):
      c[v]-=1
      if c[v]==0:
        t^=1<<v
  if r==l and l+1<=L:
    r+=1
    if P[r]:
      for v in list(map(int,str(r))):
        if c[v]==0:
          t|=1<<v
        c[v]+=1
print(ans)