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C.cpp
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C.cpp
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#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
#define ff first
#define ss second
#define rep(i, n) for(int i = 0; i < n; ++i)
#define repR(i, n) for (int i = n-1; i >= 0; --i)
#define repA(i, a, n) for (int i = a; i <= n; ++i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vs vector<string>
#define vd vector<double>
#define vb vector<bool>
#define vpii vector<pii>
#define vpll vector<pll>
#define vpdd vector<pdd>
#define mod 1000000007
#define ps(x,y) fixed << setprecision(y) << x
#define fastio ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
int Solve(vi (&v), int n, int k)
{
int ans = 0, count = 0;
if (k == 0) {
if (v[0] == 1) {
return -1;
}
else {
return 1;
}
}
rep(i, n) {
ans = v[i];
count++;
if (count == k) {
if (v[i + 1] == v[i]) {
return -1;
}
else {
return v[i];
}
}
}
return -1;
}
int main()
{
fastio
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
int n, k;
cin >> n >> k;
vi v(n);
rep(i, n) {
cin >> v[i];
}
sort(all(v));
cout << Solve(v, n, k) << '\n';
return 0;
}