#include <bits/stdc++.h>
#define rep(i, ss, ee) for (int i = ss; i < ee; ++i)
using namespace std;

void solve() {
  int N, M, x;
  cin >> N >> M;
  vector<int> v(N);
  rep(i, 0, N) v[i] = i + 1;
  rep(i, 0, M) {
    cin >> x;
    x--;
    for (int j = x; j > 0; --j) swap(v[j], v[j - 1]);
  }
  cout << v.front() << endl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
  getchar();
}