struct v2
    {
    double el[2];
    };

struct m22
    {
    double el[2][2];
    };

struct triblock22
    {
    struct v2 c[m-1];
    struct m22 a[m];
    struct v2 b[m-1];
    };

struct kvec2
    {
    struct v2 el[m];
    };

struct gvec2
    {
    struct v2 el[m-1];
    };