import sys
input = sys.stdin.readline
n = int(input())
l = [*map(int, input().split())]
while (len(l) != n):
try:
l2 = [*map(int, input().split())]
l.extend(l2)
except:
break
ans = 0
cnt = 0
mn = 11111111
for i in l:
if i % 2 == 1:
cnt += 1
if mn > i:
mn = i
ans += i
if cnt % 2 == 1:
ans -= mn
print(ans // 2)