vector<vector<int>> vd = {{0,0},{1,1},{2,2},{3,3}};
vector<vector<int>> vd2 = {{0,0},{1,-1},{2,-2},{3,-3}};
vector<vector<int>> vlr = {{0,0},{0,1},{0,2},{0,3}};
vector<vector<int>> vtb = {{0,0},{1,0},{2,0},{3,0}};
ll getD(vector<vector<int>> &v,int i,int j)
{
    vector<vector<vector<int>>> vList = {vd,vd2,vlr,vtb};
    ll mx = 0;
    for(int m = 0;m<vList.size();m++)
    {
            ll prod = 1;
            for(int k = 0;k<4;k++)
            {
                int fi = i+vList[m][k][0];
                int fj = j+vList[m][k][1];
                if(fi<20 && fj<20 && fj>=0) 
                prod = prod * (ll)v[fi][fj];
                else 
                {
                    prod = 0; break;
                }
            }
            mx = max(mx,prod); 
    }
    return mx;
}
ll greatestProd(vector<vector<int>> &v)
{
    ll mx = 0;
    for(int i = 0;i<20;i++)
    {
        for(int j = 0;j<20;j++)
        {
            mx = max(mx,getD(v, i, j));
        }
    }
    return mx;
}