include <bits/stdc++.h>

using namespace std;
int main ()
{
int n, m;
cin >> n >> m;
int a[n];
int sum = 0;
for (int i = 0; i < n; i++) {
cin >> a[i];
}
sort(a, a + n,greater<int>());
if (a[0] == 0) {
cout << "-1";
exit(0);
}
for (int i = 0; i < n; i++) {
if (i != 0) {
sum += a[i] - 1;
} else {
sum += a[i];
}
if (sum >= m) {
cout << i + 1;
exit(0);
}
}
cout << "-1";
return 0;
}