Codefroces A. Saitama Destroys Hotel

A. Saitama Destroys Hotel

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Saitama accidentally destroyed a hotel again. To repay the hotel company, Genos has volunteered to operate an elevator in one of its other hotels. The elevator is special — it starts on the top floor, can only move down, and has infinite capacity. Floors are numbered from 0 to s and elevator initially starts on floor s at time 0.

The elevator takes exactly 1 second to move down exactly 1 floor and negligible time to pick up passengers. Genos is given a list detailing when and on which floor passengers arrive. Please determine how long in seconds it will take Genos to bring all passengers to floor 0.

Input

The first line of input contains two integers n and s (1 ≤ n ≤ 100, 1 ≤ s ≤ 1000) — the number of passengers and the number of the top floor respectively.

The next n lines each contain two space-separated integers f_i and t_i (1 ≤ f_i ≤ s, 1 ≤ t_i ≤ 1000) — the floor and the time of arrival in seconds for the passenger number i.

Output

Print a single integer — the minimum amount of time in seconds needed to bring all the passengers to floor 0.

Examples

Input

3 7
2 1
3 8
5 2

Output

11

Input

5 10
2 77
3 33
8 21
9 12
10 64

Output

79

Note

In the first sample, it takes at least 11 seconds to bring all passengers to floor 0. Here is how this could be done:

1. Move to floor 5: takes 2 seconds.

2. Pick up passenger 3.

3. Move to floor 3: takes 2 seconds.

4. Wait for passenger 2 to arrive: takes 4 seconds.

5. Pick up passenger 2.

6. Go to floor 2: takes 1 second.

7. Pick up passenger 1.

8. Go to floor 0: takes 2 seconds.

This gives a total of 2 + 2 + 4 + 1 + 2 = 11 seconds.

算出每个人到0层的时间，最大值和s比较

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
using namespace std;
typedef long long ll;
int main()
{
    int n,s,a,b,max=0;
    cin>>n>>s;
    for(int i=0;i<n;i++)
    {
        cin>>a>>b;
        if(a+b>max) max=a+b;
    }
    if(s>max) cout<<s<<endl;
    else cout<<max<<endl;
    return 0;
}