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from fractions import Fraction

n, m = map(int, input().split())

inp = input()
inp = '.' + inp

# print(n, m)
# print(inp)

ans = Fraction()
idx = 1
qcount = 0
for x in inp:
  qcount += (x == '?')
# print(qcount)
while idx <= m:
  if inp[idx] == '.':
    idx += 1
    continue
  nidx = idx
  while nidx <= m and inp[nidx] != '.':
    nidx += 1
  # inp[idx..nidx - 1]
  contrib = [Fraction()] * (m + 1)
  # print("solve range", idx, nidx)
  for r in range(idx, nidx):
    c = inp[r]
    prob = Fraction(1)
    for p in range(r, -1, -1):
      dl = r - p
      if inp[p] == '?':
        # this can be end
        prob = prob / 2
        contrib[r] += prob * contrib[p - 1]
        if dl != 2 and dl != 0:
          # we can use this on for the right one
          contrib[r] += prob 
        # or continue
      elif inp[p] == '.':
        if dl != 2:
          contrib[r] += prob
        break
  # print(contrib[nidx - 1])
  ans += contrib[nidx - 1]
  idx = nidx
nume = ans.numerator
mian = ans.denominator
print('{}/{}'.format(nume, mian))