from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    N = int(input())
    A = list(map(int, input().split()))

    A.sort()
    ans = A[0]
    for i in range(1, N):
        if A[i] - 1 != A[i - 1]:
            ans += A[i]
    print(ans)


main()