vj- Bear and Strings

Bear and Strings

The bear has a string s = s1s2… 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) = sisi + 1… sj 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 sk = b, sk + 1 = e, sk + 2 = a, sk + 3 = r.

Help the bear cope with the given problem.

Input
The first line contains a non-empty string s (1 ≤ |s| ≤ 5000). It is guaranteed that the string only consists of lowercase English letters.
Output
Print a single number — the answer to the problem.

Examples
Input
bearbtear
Output
6

Intput
bearaabearc
Output
20

Note
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).

#include<stdio.h>
#include<string.h>
int main()
{
	char s[5010];
	while(scanf("%s",s)!=EOF)
	{
		int len=strlen(s);
		int count=0,repeat=0;
		for(int i=0;i<len;i++)
		{
			if(s[i]=='b'&&s[i+1]=='e'&&s[i+2]=='a'&&s[i+3]=='r')
			{
				count=count+(i+1)*(len-i-3)-repeat*(len-i-3);  
				repeat=i+1;
			}
		}
		printf("%d\n",count);
	}
 } 

如第二个例子，第一个bear，可以有1*8种，第二个bear出现时，这种算法，会将第一个bear算进去，所以要减去前一个bear的b出现时的可能。
（世の中には価値がない）