import sys
n,m,k=map(int,input().split())
table=[]
for i in range(n):
table.append(list(input()))
result=[]
for j in range(m):
middle=[]
for w in range(n):
middle.append(table[w][j])
# print(middle)
we=0
while we<n:
if middle[we]=='o':
length=0
while we<n and middle[we]=='o':
we+=1
length+=1
result.append(length)
else:
we+=1
result.sort(reverse=True)
total = 0
remaining = k
for length in result:
if remaining <= 0:
break
#判断连续染色数,看是length全染还是只染剩余remaining
use = min(length, remaining)
if use >= 2:
total += use - 1
remaining -= use
print(total)