title: Coding In AMPL Software
body: <p>How can I start with a specific city under a set of cities, rather than using x[i,j]
  I want to write such constraint x[1,2] + x[2,5] = 1</p>
  <p>Moreover, how can I start from i=2, j=2 rather than start with i,j =1</p>
  <p>Thanks,
  Haidar</p>