Memo={}
def f(x):
    if x in Memo:
        return Memo[x]

    k=0
    y=x
    while y+2 in B:
        k+=1
        y+=2

    for i in range(k+1):
        Memo[y]=i
        y-=2

    return Memo[x]

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

X=N
for a in A:
    if a+1 in B:
        X+=1
    else:
        continue

    X+=f(a+1)

print(X)