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(li i=0;i<(n);i++)
#define  red(i,n) for(li i=(n)-1;i>=0;i--)
#define  all(a)   begin(a),end(a)
#define  pb(a)    push_back(a) 
#define  fi first
#define  se second 
using namespace std;
using li = long long;
using ul = unsigned long long;
using vi = vector<li>;
using vs = vector<string>;
inline ul gcd(ul a,ul b) { return b?gcd(b,a%b):a; }
const int INF=1e9+9;


int main()
{
    int n,x,y;
    cin>>n;
    vector<pair<int,int>> a(n);
    rep(i,n) { cin>>x>>y; a.pb(make_pair(x,y)); }
    sort(all(a));
    reverse(all(a));
//    for(auto x:a)cout<<x.fi<<" "<<x.se<<endl;
    cout<<a[0].first+a[0].second<<endl;;

    
    return 0;
}