#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n, m;
    cin >> n >> m;

    vector<int> v;
    drep(i,n)v.push_back(i+1);

    rep(i,m){
        int a; cin >> a;
        v.push_back(v[n-a+i]);
    }
    cout << v[n-1+m] << endl;
    
    return 0;
}