int input min1 float inf ans for in range map int input split ans max

n = int(input())
min1 = float('inf')
ans = 0
for i in range(n):
    x,y = map(int,input().split())
    ans += max(x,y)
    if x%4 != abs(x-y)%4 and abs(x-y) < min1:
        min1 = abs(x-y)
if ans%4 == 0: print(ans-min1)
else:print(ans)