def train(stops, i, j):
new_list = []
count = 0
for e in range(0, stops):
count = count - i[e] + j[e]
new_list.append(count)
return max(new_list)
if __name__ == '__main__':
stops = int(input())
i = []
j = []
for _ in range(0, stops):
a, b = list(map(int, input().split()))
i.append(a)
j.append(b)
print(train(stops, i, j))