GAMS: How to write x(i,j) is not equal to x(i,j) as a constraint to a integer linear programming model?

Question

I thought of the equation to be

x(i,j)+x(j,i)-1 =l= 0

however, gams does not allow you to change the location of the indices. Does anyone have an idea on how to approach this?

I tried to write this

x(i,j)+x(j,i)-1 =l= 0

however, an error popped up and it would not run. Any help is appreciated