#include <fstream>
using namespace std;

int main()
{
    int i, k, n, x, suma = 0;
    ifstream fin ("grupuri.in");
    fin >> k >> n;
    for (i = 1; i <= n; i++){
        fin >> x;
        if (x < k)
            suma += x;
        else break;
        }
    k -= n - i + 1;
    ofstream fout ("grupuri.out");
    fout << suma / k;
    fout.close();
    return 0;
}