#include<iostream>
#include<fstream>
#include<cstring>
#include<algorithm>

using namespace std;

ifstream f("run.in");
ofstream g("run.out");

int di[]={1,0}; //initializare pentru avansare
int dj[]={0,1};

int ok(int i,int j,int n,int m)
{
    if(i>0&&i<=n&&j>0&&j<=m) return 1; //verificam daca am iesit din matrice
    return 0;
}
int main()
{
    long n,m,i,j,a[101][101],q[1000][2],nq,pq,k,ni,nj,l;
    char c[101][101];
    memset (a,-1,sizeof(a));
    f>>n>>m;
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
        f>>c[i][j];

        q[0][0]=1;
        q[0][1]=1;
        a[1][1]=0;

    pq=0;
    nq=1;
    while(pq<nq)
    {
        i=q[pq][0]; //pozitia liniei
        j=q[pq][1];
        for(k=0;k<2;k++)
        {
            ni=i+di[k]; //avansarea in matrice
            nj=j+dj[k];
            if(ok(ni,nj,n,m)&&c[ni][nj]=='.'&&(a[ni][nj]==-1||a[ni][nj]>a[i][j]+1))
            {
                l=max(a[ni+1][nj],a[ni][nj+1]);
                a[ni][nj]=max(a[i][j]+1,l);
                q[nq][0]=ni;
                q[nq][1]=nj;
                nq++;
            }
        }
    pq++;}
int maxi=0;
for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    if(a[i][j]>maxi) maxi=a[i][j];
g<<maxi+1;

}