#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
#define rep3(i, a, b, c) for (ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define ov4(a, b, c, d, name, ...) name
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define per(i, a, b) for (ll i = (a) - 1; i >= (b); i--)
#define fore(e, v) for (auto &&e : v)
#define all(a) begin(a), end(a)
#define sz(a) (int)(size(a))
#define lb(v, x) (lower_bound(all(v), x) - begin(v))
#define eb emplace_back

template <typename T, typename S> bool chmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> bool chmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}
const int INF = 1e9 + 100;
const ll INFL = 3e18 + 100;
#define i128 __int128_t
struct _ {
  _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); }
} __;

int main() {
  int H, W;
  cin >> H >> W;
  string S;
  cin >> S;
  vi dist(W, INF), distU(W - 1, INF);
  dist[0] = 0;
  rep(i, 1, W) {
    if (S[i] != '#')
      chmin(dist[i], dist[i - 1] + 1);
    chmin(distU[i - 1], dist[i - 1] + 1);
  }
  rep(k, H - 1) {
    cin >> S;
    vi dist2(W, INF), distU2(W, INF);
    int c = INF;
    rep(i, W) {
      chmin(c, dist[i]);
      if (S[i] != '#')
        chmin(dist2[i], dist[i] + 1), chmin(dist2[i], c + 2);
      c += 1;
    }
    c = INF;
    rep(i, W - 1) chmin(distU2[i], distU[i] + 1);
    rep(i, W - 1) {
      chmin(c, distU[i]);
      if (S[i + 1] != '#')
        chmin(dist2[i + 1], distU2[i] + 1), chmin(dist2[i + 1], c + 3);
      c += 1;
    }
    rep(i, 1, W) if (S[i] != '#') chmin(dist2[i], dist2[i - 1] + 1);
    rep(i, W - 1) chmin(distU2[i], dist2[i] + 1);
    rep(i, W) dist[i] = dist2[i];
    rep(i, W - 1) distU[i] = distU2[i];
  }
  cout << dist[W - 1] << '\n';
}