#include <iostream>
#include <vector>
#include <algorithm>

#define pb push_back
#define fi first
#define se second

using namespace std;

int main(){
    int n, m, tmp, sum = 0;
    cin >> n >> m;
    vector< pair<int, int> > d(m);
    for (int i = 0; i < m; i++){
        cin >> tmp;
        sum += tmp;
        d[i] = make_pair(tmp, i+1);
    }
    sort(d.begin(), d.end(), greater< pair<int, int> >());
    if (sum < n){
        cout << -1;
        return 0;
    }
    sum = 0;
    int k = 0;
    while (sum < n) {
        sum+=d[k].fi;
        k++;
    }
    cout << k << endl;
    for (int i = 0; i < k; i++){
        cout << d[i].se << " ";
    }
}