n=int(input())

a=[list()]*n
k=0
max=0
for i in range(0,n):
    if i==0:

        a[i].append(0)
        a[i].append(int(input()))
    elif i==n-1:
        a[i][1]=0
        a[i][0]=int(input())
    else:
        a[i]=list(map(int, input().split()))
    k+=a[i][1]-a[i][0]
    if k>max:
        max=k
print(max)