#include <fstream>

using namespace std;
ifstream fin("loto.in");
ofstream fout("loto.out");

int v[103];

int main()
{
    int n,s,i;
    fin>>n>>s;
    for(i=1;i<=n;i++)
        fin>>v[i];
    if(6*v[n]<s) fout<<"-1";
    return 0;
}