param 2n;

param c{i in 1..2n, j in 1..2n};

set S1;

var x{i in 1..2n, j in 1..2n: i<>j} >=0, <=1;

maximize Value:
	.5*sum{i in 1..2n, j in 1..2n: i<>j}c[i,j]*x[i,j];

s.t. symmetry{i in 1..2n, j in 1..2n: i<>j}:
		x[i,j]=x[j,i];

s.t. assign{i in 1..2n}:
		sum{j in 1..2n: i<>j}x[i,j]=1;

#s.t. oddsubsets: sum{i in S1, j in 1..2n diff S1} x[i,j] >= 1;

data;

param 2n:=6;

set S1:= 1 2 3;

param c[*,*]:
	1	2	3	4	5	6 :=
1	0	10	10	1	1	1
2	10	0	10	1	1	1
3	10	10	0	1	1	1
4	1	1	1	0	10	10
5	1	1	1	10	0	10
6	1	1	1	10	10	0 ;