import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)

#alist = list(map(int,input().split()))
#alist = []
#
n,m = map(int,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
s = list(input())
ans = s.count('o')
temp = []
no = 0
s.append(['x'])
for i in range(n+1):
    if s[i] != 'x':
        temp.append(s[i])
        continue
    else:
        for j in range(1,len(temp)-1):
            if temp[j-1] == 'o' and temp[j] == '-' and temp[j+1] == 'o':
                temp[j] = 'o'
                ans += 1
        for j in range(2,len(temp)):
            if temp[j-2] == 'o' and temp[j-1] == '-' and temp[j] == '-' and m:
                m -= 1
                ans += 2
                temp[j-1] == 'o'
                temp[j] = 'o'
        for j in reversed(range(len(temp)-2)):
            if temp[j+2] == 'o' and temp[j+1] == '-' and temp[j] == '-' and m:
                m -= 1
                ans += 2
                temp[j+1] == 'o'
                temp[j] = 'o'
        no += temp.count('-')
        temp.clear()
print(ans + min(no,m))