'''
贪心策略
按照si + wi 和升序排序为最佳序列
'''

n = int(input())

arr = []
for i in range(n):
    w, s = map(int, input().split())
    arr.append((w+s, w, s))

arr.sort()
S = 0
max_val = -0x7fffffff
for _, w, s in arr:
    max_val = max(max_val, S-s)
    S += w

print(max_val)