s = 'aaabbaaababbacdab'
#       **   * **    *

c = 'b'

counter = 0
i = 0
while i < len(s):
    if s[i] == c:
        counter += 1
    #print(s[i], counter)
    i += 1
print('antal forekomster af', c, 'i', s, 'er', counter)