How can I model this Eviews system of simultaneous equations in Gretl? I have trouble modelling the parameter restrictions....

 

system syscymaym4

syscymaym4.append CYMAY= C(1)+ C(2)*D_1+  C(3)*D_2+ C(4)*D_3+C(5)*D_4 +C(7)*D_6 + C(8)*D_7 + C(9)*D_8 + C(10)*D_9 + C(11)*D_10 + C(12)*D_11 + C(13)*D12 + C(14)*TTMMAY_X1  + C(15)*TMMMAY_X2 + C(16)*TMMMAY_X3 + C(17)*TMMMAY_X4

syscymaym4.append C(2)+ C(3)+c(4)+ C(5)+C(7)+C(8)+C(9)+C(10)+ C(11)+C(12)+C(13)=0