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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("3");
            WillReturn.Add("4 7");
            WillReturn.Add("2 9");
            WillReturn.Add("6 2");
            //8
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("5");
            WillReturn.Add("1 10");
            WillReturn.Add("3 6");
            WillReturn.Add("5 2");
            WillReturn.Add("4 4");
            WillReturn.Add("2 8");
            //7
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("2");
            WillReturn.Add("1 1000000000");
            WillReturn.Add("1000000000 1");
            //1000000001
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct ABInfo
    {
        internal int A;
        internal int B;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(X => int.Parse(X)).ToArray();

        var ABList = new List<ABInfo>();
        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            ABInfo WillAdd;
            WillAdd.A = wkArr[0];
            WillAdd.B = wkArr[1];
            ABList.Add(WillAdd);
        }

        ABList = ABList.OrderByDescending(X => X.A).ToList();
        Console.WriteLine(ABList[0].A + ABList[0].B);
    }
}