F. The Sum of the k-th Powerstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputThere are well-known formulas: , , . Also mathematicians found similar formulas for higher degrees.Find the value of the sum  modulo 109 + 7 (so you should find the remainder after dividing the answer by the value 109 + 7).InputThe only line contains two integers n, k (1 ≤ n ≤ 109, 0 ≤ k ≤ 106).OutputPrint the only integer a — the remainder after dividing the value of the sum by the value 109 + 7.ExamplesInput4 1Output10Input4 2Output30Input4 3Output100Input4 0Output4
Input4 1
Output10
['math', '*2600']