#include <iostream>
#include <vector>
#include <algorithm>
typedef long long ll;
using namespace std;
const int INF = 2e9;
int main() {
ios_base::sync_with_stdio(false);

ll n, K;
cin >> n >> K;

vector<ll> v(n);
for(int i = 0; i < n; i++) {
cin >> v[i];
}

ll L = 0, R = 1e18;

ll res = -1;
while(L <= R) {
ll middle = (L + R) / 2;

ll zadaci = 0;
for(int i = 0; i < n; i++) {
zadaci += middle / v[i];
}

if(zadaci >= K) {
res = middle;
R = middle - 1;
}
else {
L = middle + 1;
}
}

cout << res << endl;



return 0;
}