Background
Nikifor has decided to present the dean of the Department of Mathematics and Mechanics with a linearly independent vector system (you know, that we’ve just celebrated jubilees of the University and of the Department). A store sells M items of N-dimensional vectors, 3 ≤ N ≤ M ≤ 2000; N ≤ 50. For each vector its price ci is known, 0 < i ≤ M. Nikifor wants to buy N linearly independent vectors paying for them minimal sum of money