#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
    int m, n, ans = 0;
    cin >> m >> n;
    int arrs[n];
    for (int i = 0; i < n; i++)
    {
        scanf("%d",&arrs[i]);
        getchar();
    }
    int nums[n+m+2];
    for(int i=0;i<n;i++){
        nums[arrs[i]]=2;
    }
    int results[2];
    for(int i=m,j=0;i<n+m+2;i++){
        if(nums[i]!=2) {
            results[j]=i;
            j++;
        }
    }
    if(results[0]>results[1]){
        cout<<results[1]<<results[0]<<endl;
    }
    else {

        cout << results[0] << results[1] << endl;
    }
    return 0;
}