N = int(input())

A = list(map(int,input().split()))
A.sort()
dic = {a:0 for a in A}
for a in A[::-1]:
    dic[a] = 1
    if a+2 in dic:
        dic[a] += dic[a+2]

res = N
for a in A:
    if a+1 in A:
        res += dic[a+1]

print(res)