题目描述
Problem Statement
You are given a positive integer L in base two.
How many pairs of non-negative integers (a, b) satisfy the following conditions?
- $a + b \leq L$
- $a + b = a \text{ XOR } b$
Since there can be extremely many such pairs, print the count modulo 10^9 + 7.
What is XOR?
The XOR of integers A and $B, A \text{ XOR } B$, is defined as follows:
- When $A \text{ XOR } B$ is written in base two, the digit in the 2^k'$s place (k \geq 0)$ is 1 if either A or B, but not both, has 1 in the 2^k's place, and 0 otherwise.
For example$, 3 \text{ XOR } 5 = 6.$ (In base two: $011 \text{ XOR } 101 = 110.)$
Input
Input is given from Standard Input in the following format:
L
Output
Print the number of pairs (a, b) that satisfy the conditions, modulo 10^9 + 7.
Constraints
- L is given in base two, without leading zeros.
- $1 \leq L < 2^{100$\ 001}
Sample Input 1
10
Sample Output 1
5
Five pairs (a, b) satisfy the conditions: (0, 0), (0, 1), (1, 0), (0, 2) and (2, 0).
Sample Input 2
1111111111111111111
Sample Output 2
162261460
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分