from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N = int(input())
A = list(map(int,input().split()))

dp = defaultdict(lambda:0)
A.sort()

for a in A:
    
    dp[a+1] += 1
    
    dp[a] += dp[a-2]
    
ans = N
for a in A:
    ans += dp[a]
print(ans)