AIRPORT nco KNITRO AMPL = -10; var y{1..N} <= 10, >= -10; minimize f: sum {i in 1..N-1, j in i+1..N} ( (x[i]-x[j])^2 + (y[i]-y[j])^2 ); subject to cons1 {i in 1..N}: (x[i]-cx[i])^2 + (y[i]-cy[i])^2 - r[i] <= 0; ]]> data; param r:= 1 0.09 2 0.3 3 0.09 4 0.45 5 0.5 6 0.04 7 0.1 8 0.02 9 0.02 10 0.07 11 0.4 12 0.045 13 0.05 14 0.056 15 0.36 16 0.08 17 0.07 18 0.36 19 0.67 20 0.38 21 0.37 22 0.05 23 0.4 24 0.66 25 0.05 26 0.07 27 0.08 28 0.3 29 0.31 30 0.49 31 0.09 32 0.46 33 0.12 34 0.07 35 0.07 36 0.09 37 0.05 38 0.13 39 0.16 40 0.46 41 0.25 42 0.1; param cx:= 1 -6.3 2 -7.8 3 -9.0 4 -7.2 5 -5.7 6 -1.9 7 -3.5 8 -0.5 9 1.4 10 4.0 11 2.1 12 5.5 13 5.7 14 5.7 15 3.8 16 5.3 17 4.7 18 3.3 19 0.0 20 -1.0 21 -0.4 22 4.2 23 3.2 24 1.7 25 3.3 26 2.0 27 0.7 28 0.1 29 -0.1 30 -3.5 31 -4.0 32 -2.7 33 -0.5 34 -2.9 35 -1.2 36 -0.4 37 -0.1 38 -1.0 39 -1.7 40 -2.1 41 -1.8 42 0.0; param cy:= 1 8.0 2 5.1 3 2.0 4 2.6 5 5.5 6 7.1 7 5.9 8 6.6 9 6.1 10 5.6 11 4.9 12 4.7 13 4.3 14 3.6 15 4.1 16 3.0 17 2.4 18 3.0 19 4.7 20 3.4 21 2.3 22 1.5 23 0.5 24 -1.7 25 -2.0 26 -3.1 27 -3.5 28 -2.4 29 -1.3 30 0.0 31 -1.7 32 -2.1 33 -0.4 34 -2.9 35 -3.4 36 -4.3 37 -5.2 38 -6.5 39 -7.5 40 -6.4 41 -5.1 42 0.0; This problem is AIRPORT from the CUTEr collection.