n = int(input())
stol = list(input())
cnt = 0
flag = True
l = 0
r = len(stol) - 1
while l - r > 1:
    if flag:
        if stol[l] == 'm' and stol[r] == 'c':
            l += 1
            r -= 1
        elif stol[l] == 'm' or stol[r] == 'c':
            if stol[l] == 'm':
                l += 1
            else:
                r -= 1
        else:
            flag = False
            cnt +=1
    else:
        if stol[l] == 'c' and stol[r] == 'm':
            l += 1
            r -= 1
        elif stol[l] == 'c' or stol[r] == 'm':
            if stol[l] == 'c':
                l += 1
            else:
                r -= 1
        else:
            flag = True
            cnt += 1
print(cnt)