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: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

int main(void){
int n;
cin>>n;
vector<pair<int,int> > data(n);
for(int i=0;i<n;i++){
	int a,b;
	cin>>a>>b;
	data[i]=make_pair(a,b);
}
int amaxi=0;
sort(data.begin(),data.end());
int f=false;
for(int i=data[0].first-1;i>0;i--){
	if(data[0].second+data[0].first-i>1000000001)f++;
}
long long ans=0;
if(f>0)ans+=data[n-1].first-f;
else ans+=data[n-1].first;
ans+=data[n-1].second;
cout<<ans;
return 0;
}