#include<cstdio>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
int n, m;
char s[55][55];
vector<pair<int, int>> ed[10005]; // to,val

int id(int x, int y) {
    return x * (m + 1) + y + 1;
}

int dis[10005];
bool vis[10005];
priority_queue<pair<int, int>> Q; // -dis, pos

void dijkstra() {
    for (int i = 0;i <= n;i++) {
        for (int j = 0;j <= m;j++) {
            dis[id(i, j)] = 1e9;
        }
    }
    dis[id(0, 0)] = 0;
    Q.push({ 0, id(0, 0) });
    while (!Q.empty()) {
        int cur = Q.top().second;
        Q.pop();
        if (vis[cur]) continue;
        vis[cur] = true;
        for (auto& p : ed[cur]) {
            if (dis[p.first] > dis[cur] + p.second) {
                dis[p.first] = dis[cur] + p.second;
                Q.push({ -dis[p.first], p.first });
            }
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1;i <= n;i++) {
        for (int j = 1;j <= m;j++) {
            scanf(" %c", &s[i][j]);
        }
    }

    for (int i = 0;i <= n;i++) {
        for (int j = 0;j < m;j++) {
            ed[id(i, j)].push_back({ id(i,j + 1), (int)(s[i][j + 1] == '#') + (int)(s[i + 1][j + 1] == '#') });
            ed[id(i, j + 1)].push_back({ id(i,j), (int)(s[i][j + 1] == '#') + (int)(s[i + 1][j + 1] == '#') });
        }
    }

    for (int i = 0;i < n;i++) {
        for (int j = 0;j <= m;j++) {
            ed[id(i, j)].push_back({ id(i + 1,j), (int)(s[i + 1][j] == '#') + (int)(s[i + 1][j + 1] == '#') });
            ed[id(i + 1, j)].push_back({ id(i,j), (int)(s[i + 1][j] == '#') + (int)(s[i + 1][j + 1] == '#') });
        }
    }

    dijkstra();
    printf("%d\n", dis[id(n, m)]);
}