import sys
readline = sys.stdin.readline
from collections import Counter


N = int(readline())
A = list(map(int, readline().split()))
A.sort()
SA = set(A)
table = Counter()
ans = len(A)
for a in A:
    if a-1 in SA:
        table[a] += 1
    table[a+2] += table[a]
    ans += table[a]

print(ans)