#include <bits/stdc++.h>
using namespace std;
const int N = 510,M = 5e5+10; 
int n,m;
int f[M];
int main(){
    freopen("snow.in","r",stdin);
    freopen("snow.out","w",stdout);
    scanf("%d%d",&m,&n);
    for(int i = 1;i <= n;i++){
        for(int j = 1;j <= m;j++){
            char x;cin>>x;
            if(x == '*'){
                int l = (n - i);
                if(j-l < 1)f[1]++;
                else f[j-l]++;
                if(j+l > m)f[m+1]--;
                else f[j+l+1]--;
            }
        }
    }
    for(int i = 1;i <= m;i++)f[i] += f[i-1];
    int ans = 0;
    for(int i = 1;i <= m;i++){
//        cout<<f[i]<<endl;
        ans = max(f[i],ans);
    }
    printf("%d\n",ans);
    
    return 0;
}