from typing import List


ANSWERS = []
N = int(input())
input_list = input().split()
input_list = sorted([int(n) for n in input_list])


def geschenkt_rule(pair: List) -> bool:
    return pair[1] - pair[0] != 1


def main():
    ANSWERS.append(input_list[0])
    for n in range(1, N):
        pair: List = [input_list[n - 1], input_list[n]]
        if geschenkt_rule(pair):
            ANSWERS.append(input_list[n])

    print(sum(ANSWERS))


if __name__ == "__main__":
    main()