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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)