if __name__ == '__main__':
    n = int(input())
    q = []
    for i in range(n):
        w,s = map(int,input().split())
        q.append([w+s,w,s])

    q.sort()
    res = -float('inf')
    sum = 0
    for i in range(n):
        res = max(res,sum - q[i][2])
        sum += q[i][1]
    print(res)