#include <bits/stdc++.h>
using namespace std;
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N; long long X;
    cin >> N >> X;
    int total = 2 * N + 1;
    vector<long long> A(total);
    for(int i=0;i<N;i++){
        cin >> A[i];
    }
    vector<int> freq(N+1,0);
    for(int i=0;i<N;i++){
        if(A[i] <= N) freq[A[i]]++;
    }
    set<int> s;
    for(int x=0;x<=N;x++){
        if(freq[x]==0) s.insert(x);
    }
    for(int i = N; i < total; i++){
        int mex = *s.begin();
        A[i] = mex;
        int rem = A[i-N];
        if(rem <= N){
            freq[rem]--;
            if(freq[rem]==0) s.insert(rem);
        }
        if(mex <= N){
            if(s.find(mex)!=s.end()) s.erase(mex);
            freq[mex]++;
        }
    }
    if(X <= total) cout << A[X-1] << "\n";
    else{
        long long period = N + 1;
        long long offset = (X - N - 1) % period;
        cout << A[N + offset] << "\n";
    }
    return 0;
}