N = int(input())
A = list(map(int,input().split()))
A.sort()
from collections  import defaultdict
d = defaultdict(int)
for a in A:
    d[a] += 1
for a in reversed(A):
    if a - 2 in d:
        d[a-2] += d[a]
ans = 0
for a in A:
    ans += 1 + d[a+1]
print(ans)