#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <utility>
#include <list>
#include <functional>
#include <queue>
#include <map>
#include <iterator>
#include <iomanip>
#include <complex>
using namespace std;

using ull = unsigned long long;
using ll = long long;


int main()
{
  int n,m;
  cin >> n >> m;
  int pos = 1;

  vector<int> shl(m);

  for(auto&& x : shl) cin >> x;

  for(int i = m-1; i >= 0; --i)
  {
    if(pos == 1)
      pos = shl.at(i);
    else if(shl[i] >= pos)
      --pos;
  }

  cout << pos << endl;

}