N = int(input())
A = list(map(int,input().split()))
A.sort()
ans = 0
now= 0
dp = [[0,0] for _ in range(3)]
for i in range(N):
    if now +1 == A[i]:
        dp = dp[1:] + [[0,0]]
    elif now +2 == A[i]:
        dp = dp[2:] + [[0,0] ,[0,0]]
    else:
        dp = [[0,0] ,[0,0],[0,0]]
    dp[1][0] = 1
    ans += 1 + sum(dp[0])
    dp[2][1] = sum(dp[0])
    now = A[i]

print(ans)