Gauss

int n ,tot[MAX],pos[MAX]; double edge[MAX][MAX],res[MAX];vector<pii>v[MAX];


int gauss(int row,int col)
{
    mem(pos,-1);
    int free_var = 0;
    for(int i = 1,j = 1;i<=row,j<=col;i++,j++)
    {
        int mx = i;
        for(int k = i;k<=row;k++)if(abs(edge[mx][j])<abs(edge[k][j]))  mx = k;
        if(abs(edge[mx][j])>EPS)
        {
            pos[j] = i;
            for(int l = j;l<=col;l++)swap(edge[i][l],edge[mx][l]);
            for(int l = 1;l<=row;l++)
            {
                if(l==i)continue;
                double xx = edge[l][j] / edge[i][j];
                for(int pp = j;pp<=col;pp++)edge[l][pp]-=(edge[i][pp]*xx);
            }

        }
    }

    for(int l = 1;l<col;l++)
    {
        if(pos[l]==-1)free_var++;
        else res[l] = edge[pos[l]][col]/edge[pos[l]][l];
    }
    for(int i = 1;i<=row;i++)
    {
        double val = 0.0;
        for(int j = 1;j<col;j++)val+=(res[j]*edge[i][j]);
        if(abs(val - edge[i][col])>EPS)return -1;
    }
    return free_var;
}