N = int(input())

A = list(map(int,input().split()))
A.sort()
data = [1 for i in range(N)]
for i in range(N-2,-1,-1):
    if i+1<N and A[i+1]==A[i]+2:
        data[i] += data[i+1]
    elif i+2<N and A[i+2]==A[i]+2:
        data[i] += data[i+2]

res = N
for i in range(N-2,-1,-1):
    if A[i+1]==A[i]+1:
        res += data[i+1]

print(res)