B'Devu is a renowned classical singer. He is invited to many big functions/festivals. Recently he was invited to "All World Classical Singing Festival". Other than Devu, comedian Churu was also invited. Devu has provided organizers a list of the songs and required time for singing them. He will sing n songs, ith song will take ti minutes exactly. The Comedian, Churu will crack jokes. All his jokes are of 5 minutes exactly. People have mainly come to listen Devu. But you know that he needs rest of 10 minutes after each song. On the other hand, Churu being a very active person, doesn 't need any rest. You as one of the organizers should make an optimal s xd1 x81hedule for the event. For some reasons you must follow the conditions: If it is not possible to find a way to conduct all the songs of the Devu, output -1. Otherwise find out maximum number of jokes that Churu can crack in the grand event. The first line contains two space separated integers n, d (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89100; 1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89d xe2 x80 x89 xe2 x89 xa4 xe2 x80 x8910000). The second line contains n space-separated integers: t1, xe2 x80 x89t2, xe2 x80 x89..., xe2 x80 x89tn (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ti xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89100). If there is no way to conduct all the songs of Devu, output -1. Otherwise output the maximum number of jokes that Churu can crack in the grand event. Consider the first example. The duration of the event is 30 minutes. There could be maximum 5 jokes in the following way: Total time spent is 5 xe2 x80 x89+ xe2 x80 x892 xe2 x80 x89+ xe2 x80 x8910 xe2 x80 x89+ xe2 x80 x892 xe2 x80 x89+ xe2 x80 x8910 xe2 x80 x89+ xe2 x80 x891 xe2 x80 x89= xe2 x80 x8930 minutes. Consider the second example. There is no way of organizing Devu 's all songs. Hence the answer is -1. '...