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