import math

if __name__ == '__main__':
    N = int(input())
    x = list(map(int, input().split()))
    SUM = 0
    for i in range(N):
        SUM += x[i] // 2
    if max(x) % 2 == 1:
        SUM += int(math.ceil(max(x)))
    else:
        SUM += max(x) // 2
    print(SUM)