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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>

#define rep(i, n) for(int i = 0; i < (n); i++)
#define all(a) (a).begin(),(a).end()
#define SORT(a) sort(all(a))
#define rSORT(a, i) sort(all(a),(i))

using ll = long long;
constexpr ll INF = 10000000000;
constexpr ll MOD = 1000000007;

using namespace std;

int main() {
	ll n; cin >> n;

	ll max_a = 0;
	ll aiueoon = 0;
	for (int i = 0; i < n; i++) {
		int x, y;
		cin >> x >> y;

		if (max_a < x) {
			max_a = x;
			aiueoon = y;
		}
	}
	cout << max_a + aiueoon << endl;
}