from re import I
n, m, k = map(int,input().split())
l = []
for i in range(n):
    l1 = list(input().split())
    l += l1
l2 = []
for i in range(m):
    c = 0
    for j in range(n):
        if l[j][i] == '*':
            l2.append(c)
            c = 0
        else:
            c += 1
    l2.append(c)
s = 0
l2.sort(reverse=True)
for i in l2:
    if k > i:
        s += i - 1
        k -= i
    else:
        s += k - 1
        break
print(s)