import sys

input = sys.stdin.buffer.readline

N = int(input())
A = sorted(map(int, input().split()))
d = {a: i for i, a in enumerate(A)}
table2 = [0] * N
ans = N
for i in range(N - 1, -1, -1):
    if A[i] + 2 in d:
        table2[i] = table2[d[A[i] + 2]] + 1
    if A[i] - 1 in d:
        ans += table2[i] + 1
print(ans)