Patching Array


Can anyone help to explain more about this statement "suppose the k patches found by greedy algorithm is X_1 < X_2 <... ≤ X_k ≤ n. If there is another set of patches Y_1 ≤ Y_2 ≤...≤ Y_{k'} ≤n, with k'<k, then we have Y_1 <= X_1, otherwise X_1 is not covered."
More specifically, how to deduce inequality of “Y_1 <= X_1” ？ Given n , k' patches, we could only know X_k <=n and Y_k' <=n and k'<k, but I can't see where we could get “Y_1 <= X_1”.
Thanks!

Can anyone help to explain more about this statement "suppose the k patches found by greedy algorithm is X_1 < X_2 <... ≤ X_k ≤ n. If there is another set of patches Y_1 ≤ Y_2 ≤...≤ Y_{k'} ≤n, with k'<k, then we have Y_1 <= X_1, otherwise X_1 is not covered."
More specifically, how to deduce inequality of “Y_1 <= X_1” ？ Given n , k' patches, we could only know X_k <=n and Y_k' <=n and k'<k, but I can't see where we could get “Y_1 <= X_1”.
Thanks!