排序尽可能在染色所有列中比较长的"o"段,每次染色计分可以染色的个数-1

n,m,k  = map(int,input().split())
maps = [""]*m
ans=0
for _ in range(n):
    map = input()
    for i in range(m):
        maps[i] += map[i]
duan = []
for s in maps :
    s = s.split("*")
    for i in s :
        if i :
            duan.append(len(i))
duan.sort(reverse=True)
for i in duan :
    if k > i :
        ans += i-1
        k -= i
    else :
        ans += k-1
        break
print(ans)