#include<bits/stdc++.h>
using namespace std;

int main(){
    int N,M,in;
    vector<int> v;

    cin >> N >> M;
    for(int i=N;i>0;i--) v.push_back(i);
    while(cin >> in){
        int select=v[v.size()-in];
        v.erase(v.end()-in);
        v.push_back(select);
    }
    cout << v.back() << endl;

    return 0;
}