import sys
from collections import defaultdict
sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N = I()
A = LI()
A.sort()
d = defaultdict(int)
for a in A:
    d[a] = 1

flag = defaultdict(int)
for a in A:
    flag[a] = 0

for a in A:
    if flag[a] == 0:
        b = a
        while d[b] == 1:
            b += 2
        r = (b-a)//2
        for i in range(a,b,2):
            flag[i] = r-(i-a)//2

ans = N
for a in A:
    ans += flag[a+1]

print(ans)