n=int(input())
ns=[int(input()) for i in range(n)]
ns.sort(reverse=True)
lis=[0]*n
cnt=0

def  cal(x):
    lis[x]=1
    now = ns[x]
    for i in range(n):
        if lis[i] == 1:
            continue
        if now > ns[i]+1:
            now = ns[i]
            lis[i] = 1


for i in range(n):
    if lis[i] == 0:
        cal(i)
        cnt+=1
    

                    
print(cnt)