#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)

INF = 10**10
N = int(input())
A = list(map(int, input().split()))

s = set(A)
ans = 0
for a in A:
    if a-1 not in s:
        ans += a
print(ans)