from math import inf


def get_len(arr):
    count = 0
    for elem in arr:
        if elem != 0:
            count += 1
    return count


def find_min(n, arr):
    ind = 0
    m = inf
    for i in range(n):
        if arr[i] < m and arr[i] != 0:
            m = arr[i]
            ind = i
    return ind


def find_max(n, arr):
    ind = 0
    m = -inf
    for i in range(n):
        if arr[i] >= m and arr[i] != 0:
            m = arr[i]
            ind = i
    return ind


def solution(n, arr):
    count = 0
    while get_len(arr) > 1:
        min_elem_ind = find_min(n, arr)
        max_elem_ind = find_max(n, arr)
        if arr[min_elem_ind] == arr[max_elem_ind]:
            count += arr[min_elem_ind]
            arr[min_elem_ind] = 0
            arr[max_elem_ind] = 0
        else:
            arr[min_elem_ind] -= 1
            arr[max_elem_ind] -= 1
            count += 1
    return count


n = int(input())
arr = list(map(int, input().split()))
print(solution(n, arr))