#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<utility>
#include<sstream>
#include<cctype>
#include<cmath>
#include<algorithm>
using namespace std;

#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define repp(i,n) for(int (i)=1;(i)<=(n);(i)++)
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define clr(a) memset((a), 0 ,sizeof(a))


typedef pair<int,int> P;
typedef vector<pair<int,string> > pii;
typedef map<string,int> mi;




int main(){
	int n,k;
	vector<int> vc;
	cin >> n >> k;
	for(int i=0;i<=n;i++) vc.push_back(i);
	rep(i,k){
		int a;
		cin >> a;
		swap(vc[0],vc[a]);
		vc.erase(vc.begin()+a);
		vc.insert(vc.begin(),0);
	}
	cout << vc[1] << endl;
	return 0;
}