A group of people played a game. All players had distinct scores, which are positive integers.

Takahashi knows N facts on the players' scores. The i-th fact is as follows: the A_i-th highest score among the players is B_i.

Find the maximum possible number of players in the game.

Constraints

* 1 \leq N \leq 10^5
* 1 \leq A_i \leq 10^9(1\leq i\leq N)
* 0 \leq B_i \leq 10^9(1\leq i\leq N)
* If i ≠ j, A_i ≠ A_j.
* There exists a possible outcome of the game that are consistent with the facts.
* All input values are integers.

Inputs

Input is given from Standard Input in the following format:


N
A_1 B_1
:
A_N B_N


Outputs

Print the maximum possible number of players in the game.

Examples

Input

3
4 7
2 9
6 2


Output

8


Input

5
1 10
3 6
5 2
4 4
2 8


Output

7


Input

2
1 1000000000
1000000000 1


Output

1000000001
n = input()

a = []
b = []

count = 0

for i in range(n):
    a_,b_ =[int(i) for i in raw_input().split()]
    a.append(a_)
    b.append(b_)
    

c = zip(a,b)
c.sort()
a, b = zip(*c)
a = list(a)
b = list(b)

before_rank = 1
before_score = 10000000000
for i in range(n):

    count += min(a[i]-before_rank, before_score-b[i])
    before_rank = a[i]
    before_score = b[i]

count += before_score + 1


print(count)
