#include <iostream>
#include <vector>
using namespace std;

int main()
{
    int n,m;
    cin >> n >> m;

    int a;
    vector<int> x(n);
    for(int i = 0; i < n; i++) x[i] = n - i;
    for(int i = 0; i < m; i++){
        cin >> a;
        x.push_back(x[n-a]);
        x.erase(x.begin()+n-a);
    }

    cout << x[n-1] << endl;

    return 0;
}