Bear and Strings

题面翻译

给定一个字符串，找出所有的子串$\ s_{i}s_{i+1}...s_{j}$，该子串包含 $\ bear$这个单词,输出满足条件的子串个数。

题目描述

The bear has a string $s=s_{1}s_{2}...\ s_{|s|}$ (record $|s|$ is the string's length), consisting of lowercase English letters. The bear wants to count the number of such pairs of indices $i,j$ $(1<=i<=j<=|s|)$ , that string $x(i,j)=s_{i}s_{i+1}...\ s_{j}$ contains at least one string "bear" as a substring.

String $x(i,j)$ contains string "bear", if there is such index $k$ $(i<=k<=j-3)$ , that $s_{k}=b$ , $s_{k+1}=e$ , $s_{k+2}=a$ , $s_{k+3}=r$ .

Help the bear cope with the given problem.

输入格式

The first line contains a non-empty string $s$ $(1<=|s|<=5000)$ . It is guaranteed that the string only consists of lowercase English letters.

输出格式

Print a single number — the answer to the problem.

样例 #1

样例输入 #1

bearbtear

样例输出 #1

6

样例 #2

样例输入 #2

bearaabearc

样例输出 #2

20

提示

In the first sample, the following pairs $(i,j)$ match: $(1,4),(1,5),(1,6),(1,7),(1,8),(1,9)$ .

In the second sample, the following pairs $(i,j)$ match: $ (1,4),(1,5),(1,6),(1,7),(1,8),(1,9),(1,10),(1,11),(2,10),(2,11),(3,10),(3,11),(4,10),(4,11),(5,10),(5,11),(6,10),(6,11),(7,10),(7,11) $ .