[bronze3]백준 2460번.

arr=[]

for i in range(1,11):
    a, b = input().split()
    c=int(a)
    d=int(b)
    e= d-c
    arr.append(e)

# print(arr)

for j in range(1,10):
    f=arr[j]+arr[j-1]
    arr[j]=f

# print(arr)
print(max(arr))