Complex qqgamgam_tree_mpmp(int i1, int i2, int i3, int i4) { return pow(spa(i1,i3),2)/spa(i1,i4)/spa(i2,i4); }
Complex qqgamgam_tree_pmpm(int i1, int i2, int i3, int i4) { return pow(spb(i1,i3),2)/spb(i1,i4)/spb(i2,i4); }

Complex qqgamgam_tree_gen(int i1, int h1, int i2, int i3, int h3, int i4, int h4) {
    if ( h3==h4 ) return 0;
    else if ( h1==h3 ) {
        if ( h1==1 ) return qqgamgam_tree_pmpm(i1,i2,i3,i4);
        else return qqgamgam_tree_mpmp(i1,i2,i3,i4);
    }
    else { // h1==h4
        if ( h1==1 ) return qqgamgam_tree_pmpm(i1,i2,i4,i3);
        else return qqgamgam_tree_mpmp(i1,i2,i4,i3);
    }
}


// q(1) qbar(2) -> gam(3) gam(4)
Complex qqbgamgam_tree(int h1, int h3, int h4) { return qqgamgam_tree_gen(1,h1,2,3,h3,4,h4); }
// qbar(1) q(2) -> gam(3) gam(4)
Complex qbqgamgam_tree(int h2, int h3, int h4) { return qqgamgam_tree_gen(2,h2,1,3,h3,4,h4); }