Time Limit: 2 seconds
Memory Limit: 256 megabytes
There 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).
Print the only integer a — the remainder after dividing the value of the sum by the value 109 + 7.