param n:=8;

set V:={1..n};
set W:={1..(2*n)};

var x[V*V] binary;

maximize fobj: sum<i,j> in V*V: x[i,j];

subto c1: forall<i> in V: sum<j> in V: x[i,j]<=1;
subto c2: forall<j> in V: sum<i> in V: x[i,j]<=1;
subto c3: forall<k> in W: sum<i,j> in V*V with i+j==k: x[i,j]<=1;
subto c4: forall<k> in W: sum<i,j> in V*V with i-j+n==k: x[i,j]<=1;