param n;
param m;

param is_element_of{i in 1..n, j in 1..m};
var x{j in 1..m}, binary;

minimize total: sum{j in 1..m} x[j];
s.t. coverage_constraints {i in 1..n}: sum{j in 1..m} is_element_of[i,j]*x[j] >= 1;
s.t. nonnegative {j in 1..m}: x[j] >=0;

data;

param n:=6;
param m:=6;

param is_element_of:  
   1 2 3 4 5 6 :=
1  1 0 1 0 0 1
2  1 0 0 1 0 0
3  0 1 1 1 0 1
4  1 1 0 0 1 0
5  0 1 0 1 1 0
6  0 0 1 0 1 0;
end;