#include <bits/stdc++.h>

using namespace std;

int main(){
    int n, m;
    while(cin >> n >> m, n+m){
        vector<int> f, s, v;
        bool white = false;
        for(int i=0; i < m; i++){int t; cin >> t; if(t != 0) v.push_back(t); else white = true;}
        sort(v.begin(), v.end());
        f.push_back(v[0]); s.push_back(v[0]);
        for(int i=1; i< v.size(); i++){
            if(s[s.size()-1] == v[i]-1) s[s.size()-1] = v[i];
            else {f.push_back(v[i]); s.push_back(v[i]);}
        }
        int ret = 0;
        if(white){
            for(int i=0; i < s.size()-1; i++){
                if(s[i]+2 == f[i+1]) ret = max(ret, s[i]-f[i]+2+s[i+1]-f[i+1]+1);
            }
        } else {
            for(int i=0; i < s.size(); i++){
                ret = max(ret, s[i]-f[i]+1);
            }
        }
        cout << ret << endl;
    }
}
### Prompt

Please create a solution in CPP to the following problem:

problem

There are n cards with one integer from 1 to n and one blank card. Of these n + 1 cards, k cards are given, but 1 ≤ k ≤ n. You can write one integer from 1 to n on a blank card. I want to make a continuous sequence of integers as long as possible with just a given card.

Write a program that outputs the maximum length of a contiguous sequence of integers that can be made from a given card when the given card is entered.



input

The input consists of multiple datasets. Each dataset is given in the following format. The input ends on a line containing two zeros.

On the first line, two integers n (1 ≤ n ≤ 100000) and k (1 ≤ k ≤ n) are written in this order, separated by one blank. The following k line contains one integer. Written one by one, representing the integers written on the given k cards. Blank cards are represented by 0.

Of the scoring data, 40% of the points are 1 ≤ n ≤ 1000, 1 ≤ k ≤ 500, 20% of the points are 1 ≤ n ≤ 60000, 1 ≤ k ≤ 50000. Satisfy 1 ≤ n ≤ 100000, 1 ≤ k ≤ 100000.

The number of datasets does not exceed 5.

output

Outputs an integer on one line for each dataset.

Examples

Input

7 5
6
2
4
7
1
7 5
6
2
0
4
7
0 0


Output

2
4


Input

None


Output

None

### Response

```cpp
#include <bits/stdc++.h>

using namespace std;

int main(){
    int n, m;
    while(cin >> n >> m, n+m){
        vector<int> f, s, v;
        bool white = false;
        for(int i=0; i < m; i++){int t; cin >> t; if(t != 0) v.push_back(t); else white = true;}
        sort(v.begin(), v.end());
        f.push_back(v[0]); s.push_back(v[0]);
        for(int i=1; i< v.size(); i++){
            if(s[s.size()-1] == v[i]-1) s[s.size()-1] = v[i];
            else {f.push_back(v[i]); s.push_back(v[i]);}
        }
        int ret = 0;
        if(white){
            for(int i=0; i < s.size()-1; i++){
                if(s[i]+2 == f[i+1]) ret = max(ret, s[i]-f[i]+2+s[i+1]-f[i+1]+1);
            }
        } else {
            for(int i=0; i < s.size(); i++){
                ret = max(ret, s[i]-f[i]+1);
            }
        }
        cout << ret << endl;
    }
}
```