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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict";
const main = arg => {
  let Info = arg.split("\n");
  let Num = Info.shift();
  // .map(x => x*1)については型変換の常套句
  let personInfo = Info.map(i => i.split(" ").map(x => x*1));
  let infoMap = new Map();
  let As = [];
  
  // 情報をそれぞれの値に格納する（別にmapでなくてもよかった）
  personInfo.forEach((x) => {
  	infoMap.set(x[0],x[1]); 
    As.push(x[0]);
  })
  // 一番最下位に近い人とその人の下に何人いるかの可能性だけ探ればいい
  let Amax = Math.max(...As);
  let ans = Amax + infoMap.get(Amax);
  
  console.log(ans);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));