#include <iostream>

using namespace std;

char a[105][105];
int dp[105][105];

int main()
{
    int i,j,N,M,maxim;
    cin>>N>>M;
    for(i=1;i<=N;++i)
        for(j=1;j<=M;++j)
            cin>>a[i][j];
    for(i=1;i<=N;++i)
        for(j=1;j<=M;++j)
            if(a[i][j]=='&')
                dp[i][j]=0;
            else
                dp[i][j]=max(dp[i-1][j], dp[i][j-1])+1;
    maxim=0;
    for(i=1;i<=N;++i)
        for(j=1;j<=M;++j)
            maxim=max(maxim,dp[i][j]);
    cout<<maxim;
    return 0;
}