B'Little Petya very much likes strings. Recently he has received a voucher to purchase a string as a gift from his mother. The string can be bought in the local shop. One can consider that the shop has all sorts of strings over the alphabet of fixed size. The size of the alphabet is equal to k. However, the voucher has a string type limitation: specifically, the voucher can be used to purchase string s if the length of string 's longest substring that is also its weak subsequence (see the definition given below) equals w. String a with the length of n is considered the weak subsequence of the string s with the length of m, if there exists such a set of indexes 1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89i1 xe2 x80 x89< xe2 x80 x89i2 xe2 x80 x89< xe2 x80 x89... xe2 x80 x89< xe2 x80 x89in xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m, that has the following two properties: Petya got interested how many different strings are available for him to purchase in the shop. As the number of strings can be very large, please find it modulo 1000000007 (109 xe2 x80 x89+ xe2 x80 x897). If there are infinitely many such strings, print "-1". The first line contains two integers k (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89k xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89106) and w (2 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89w xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109) -- the alphabet size and the required length of the maximum substring that also is the weak subsequence, correspondingly. Print a single number -- the number of strings Petya can buy using the voucher, modulo 1000000007 (109 xe2 x80 x89+ xe2 x80 x897). If there are infinitely many such strings, print "-1" (without the quotes). In the first sample Petya can buy the following strings: aaa, aab, abab, abb, abba, baa, baab, baba, bba, bbb.'...