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
{
    public static bool f = false, t = true;
    static void Main(string[] args)
    {
        long n = long.Parse(Console.ReadLine());
        long ans = 0;
        long max = 0, maxguy = 0;
        long min = int.MaxValue, minguy =0;
        for (long i = 0; i < n; i++)
        {
            long[] s = Read.longs();
            if (s[1] > max) { max = s[1]; maxguy = s[0]; }
            if (s[1] < min) { min = s[1]; minguy = s[0]; }

        }
        ans = min  + maxguy - 1;

        Console.WriteLine(ans+minguy-maxguy+1);
        Console.ReadLine();

        /*  int n = int.Parse(Console.ReadLine());
          for(int i = 1; i <= 1750; i++)
          {
              for (int j = 1; j <= 1750; j++)
              {
                  for (int k = 1; k <= 1750; k++)
                  {
                      if (n * (i * j + j * k + i * k) == 4 * i * j * k)
                      {
                          Console.WriteLine(i + " " + j + " " + k);
                          Console.ReadLine();
                          return;
                      }
                      int j1 = 3501 - j;
                      int i1 = 3501 - i;
                      int k1 = 3501 - k;
                      if (n * (i1 * j1 + j1 * k1 + i1 * k1) == 4 * i1 * j1 * k1)
                      {
                          Console.WriteLine(i1 + " " + j1 + " " + k1);
                          Console.ReadLine();
                          return;
                      }

                  }
              }
          }*/
    }

    public static long gcd(long a, long b)
    {
        while (true)
        {
            if (a == 0) { return b; }
            if (b == 0) { return a; }
            if (a > b) { a -= b; }
            else { b -= a; }
        }
    }
    public static long lcm(long a, long b)
    {
        return a / gcd(a, b) * b;
    }
    public static bool IsPrime(long n)
    {
        if (n < 2) return false;
        if (n == 2) return true;

        for (long i = 2; i < n; i++)
        {
            if (n % i == 0) return false;
        }
        return true;
    }

}
public static class Read
{
    public static void outl(string n = "") { Console.WriteLine(n); return; }
    public static long Long()
    {
        return long.Parse(Console.ReadLine());
    }
    public static long[] longs()
    {
        return Console.ReadLine().Split().Select(long.Parse).ToArray();
    }
    public static int Int()
    {
        return int.Parse(Console.ReadLine());
    }
    public static int[] ints()
    {
        return Console.ReadLine().Split().Select(int.Parse).ToArray();
    }
    public static string Str() { return Console.ReadLine(); }
    public static string[] Strs() { return Console.ReadLine().Split(); }
}