#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;


int main() {

    int N, M;
    cin >> N >> M;

    vector<int> as;
    for (int i = 0; i < M; ++i) {
        int a;
        cin >> a;
        as.push_back(a);
    }
    int i = 1;
    for (int k = M - 1; k >= 0; --k) {
        if (i == 1) {
            i = as[k];
            continue;
        }
        if (as[k] < i) {
            continue;
        } else {
            i = i - 1;
        }
    }

    cout << i << endl;

    return 0;
}