概率可能性的计算的一个算法，怎么使用C语言的程序的编写的过程步骤去实现的呢

Question

Problem Description
Mickey is interested in probability recently. One day , he played a game which is about probability with mini.First mickey gives a letter and a word to mini.Then mini calculate the probability that the letter appears in the word.For example,give you the letter "a" and the word "apple". the probability of this case is 0.20000.

Input
The input contains several test cases. Each test case consists of a letter and a word.The length of the word is no longer than 200.

Output
For each test case, print the probability rounded to five digits after the decimal point.

Sample Input
a apple
c Candy
a banana

Sample Output
0.20000
0.20000
0.50000