Problem:
Score : 200 points

Problem Statement

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.

Sample Input 1

3
4 7
2 9
6 2

Sample Output 1

8

The maximum possible number of players is achieved when, for example, the players have the following scores: 12,9,8,7,5,2,1,0.

Sample Input 2

5
1 10
3 6
5 2
4 4
2 8

Sample Output 2

7

Sample Input 3

2
1 1000000000
1000000000 1

Sample Output 3

1000000001

Solution in Ruby (2.7.1) (judge verdict: Accepted)


#知っている情報の中での最高得点者と最低得点者を考える。
#最高得点者がM番目であるなら、上には高々M-1人しかいない。
#最低得点者がL点であるなら、下には高々L人しかいない。
#よって、回答は、
#(M-1)+{(最低得点者の席次)-M+1}+(L-1)=(最低得点者の席次) + L
#最低得点者の情報だけ分かればよい。
n = gets.to_i
b_min = (10 ** 9) + 1
i = 0
x = (10 ** 9) + 1 
while i < n
  a,b = gets.chomp.split(' ').map(&:to_i)
  if b < b_min
    b_min = b
    x = a
  end
  i += 1
end
puts x + b_min