#include <iostream>
#include<string>

using namespace std;
using ll = long long int;
int main(void){
    int n, m, atmp;
    cin >> n >> m;
    int a[m];
    for (int i = 0; i < m; i ++){
        cin >> atmp;
        a[i] = atmp - 1;
    }
    int now = 0;
    for (int i = m - 1; i >= 0; i--){
        if (now == 0){
            now = a[i];
        }
        else if (now < a[i]){
            now --;
        }
    }
    cout << now + 1 << endl;
    return 0;
}