题解 | 小红的二叉树
小红的二叉树
https://www.nowcoder.com/practice/ee287e0f6af64edd969f01444dd763e4
n = int(input()) if n == 1: print(0) else: pow1 = pow(2,n-1,1000000007) print((3*pow1-5)%1000000007)
小红的二叉树
https://www.nowcoder.com/practice/ee287e0f6af64edd969f01444dd763e4
n = int(input()) if n == 1: print(0) else: pow1 = pow(2,n-1,1000000007) print((3*pow1-5)%1000000007)
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