#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
#define N 1001
#define NN 1005000
#define PB push_back
#define M ll(1e9 + 7)
#define all(x) x.begin(), x.end()
#define sz(x) int(x.size())
#define pri(x) cout << x << endl
#define endl '\n'
#define _ << " " <<
#define F first
#define S second
using namespace std;
//using namespace __gnu_pbds;
//typedef tree <int, null_type, less <int>, rb_tree_tag, tree_order_statistics_node_update> oredered_set;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef short int si;
int f[N][(1 << 10)], kol[N][(1 << 10)];
int main()
{
ios_base::sync_with_stdio(0); istream::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// freopen("1.in", "r", stdin);
int n, m;
cin >> n >> m;
string s[n];
int mask[n];
for (int i = 0; i < n; i++)
{
cin >> s[i];
mask[i] = 0;
for (int j = 0; j < m; j++)
if (s[i][j] == '.')
mask[i] |= (1 << j);
for (int j = 0; j < (1 << m); j++)
{
kol[i][j] = 0;
int p = 0;
for (int u = 0; u < m; u++)
{
if (s[i][u] == '.' || ((1 << u) & j))
{
p = 0;
continue;
}
p++;
if (p == 1)
kol[i][j]++;
}
}
}
for (int i = 0; i <= n; i++)
for (int j = 0; j < (1 << m); j++)
f[i][j] = 1e9;
f[0][0] = 0;
for (int i = 0; i < n; i++)
{
for (int j = (1 << m) - 1; j >= 0; j--)
for (int k = 0; k < m; k++)
if ((1 << k) & j)
f[i][j ^ (1 << k)] = min(f[i][j ^ (1 << k)], f[i][j]);
for (int j = 0; j < (1 << m); j++)
for (int k = 0; k < m; k++)
{
if ((1 << k) & j) continue;
f[i][j ^ (1 << k)] = min(f[i][j ^ (1 << k)], f[i][j] + 1);
}
for (int j = 0; j < (1 << m); j++)
{
if (__builtin_popcount(j & mask[i]) > 0)
continue;
f[i + 1][j] = min(f[i + 1][j], f[i][j] + kol[i][j]);
}
}
int ans = 1e9;
for (int msk = 0; msk < (1 << m); msk++)
ans = min(ans, f[n][msk]);
pri(ans);
}
