#Write a function countTriGrams(s,trigram) that takes
#two strings as parameters.
#The second string is of length 3.

#The function should count the number of (possibly overlapping)
#occurrences of the string trigram within s.
#For example, countTriGrams("mississippi", "iss") should return 2.

def countTriGrams(s, trigram):
    count = 0
    for i in range(len(s)-2):
        if s[i:i+3] == trigram:
            count += 1

    return count