#include<bits/stdc++.h>
using namespace std;
long long n,K,a[200005],x,y,k,t;
map<long long,bool>mp;
int main(){
	freopen("ntarsis_set.in","r",stdin);
	freopen("ntarsis_set.out","w",stdout); 
	cin>>n>>K;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		mp[a[i]]=1;
	}
	if(a[1]>1){
		cout<<1;return 0;
	}
	long long ki=0;
	while(++ki){
		if(mp[ki]){
			k++;continue;
		}
		break;
	}
	K--; 
	while(K){
//		cout<<ki<<" "<<k<<endl; 
//		cout<<mp[ki+k]<<" "<<a[k+1]<<endl;
		if((mp[ki+k]==0&&ki+k<a[k+1])||k==n){
			ki+=k;
		}else{
			k++;
			continue;
		}
		K--;
	}
	cout<<ki;
	return 0;
}