import sys
input = sys.stdin.buffer.readline


def main():
    N = int(input()); INF = pow(10,18)
    A = [-INF] + list(map(int,input().split()))
    A.sort()
    ans = 0
    for i in range(1,N+1):
        if A[i-1] + 1 == A[i]: continue
        ans += A[i]
    print(ans)
    

if __name__ == '__main__':
    main()