#include <bits/stdc++.h>

using namespace std;

int main()
{
    int N, M; cin >> N >> M;
    vector<int> C(N);
    for (int i = 0; i < N; ++i) C[i] = N - i;
    while (M--) {
        int A; cin >> A;
        int a = C[N-A];
        C.erase(C.begin()+N-A);
        C.push_back(a);
    }
    cout << C[N-1] << endl;
}