mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    N = int(input())
    A = list(map(int, input().split()))
    A_set = set(A)
    dic = {}
    for a in A:
        dic[a] = 1
        if a-1 not in dic:
            dic[a-1] = 0
        if a+1 not in dic:
            dic[a+1] = 0
    B = list(dic.keys())
    B.sort()
    ans = 0
    for i in range(1, len(B)):
        if B[i] - 1 in A_set:
            dic[B[i]] += dic[B[i] - 2]
        ans += dic[B[i]]
    print(ans)


if __name__ == '__main__':
    main()