n = int(input())
A = []
for _ in range(n):
    a, b = map(int, input().split())
    A.append((a, b - a))
A.sort()
ans = max(A[i - 1][1] + A[i][0] for i in range(1, n))
def f(num, l, max_A):
    global ans
    if max_A >= ans:
        return
    if l == 0:
        ans = max_A
        return
    for i in range(n):
        if (1 << i) & l:
            max_A = max(max_A, A[num][1] + A[i][0])
            f(i, l - (1 << i), max_A)
for i in range(n):
    f(i, ((1 << n) - 1) - (1 << i), 0)
print(ans)