var 1..100: Children :: output_var;
var 1..100: Grandparents :: output_var;
var 1..100: Parents :: output_var;
constraint int_lin_eq([1, 1, 1], [Children, Grandparents, Parents], 20);
constraint int_lin_eq([1, 6, 4], [Children, Grandparents, Parents], 40);
solve satisfy;