#include<bits/stdc++.h>
using namespace std;
int n, m;
bool vis[1005][1005];
string maze[1005];
int ans, cnt;
int dir[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
bool in(int x, int y) {
return x >= 0 && x < n && y >= 0 && y < m;
}
void dfs(int x, int y) {
cnt++;
vis[x][y] = true;
for (int i = 0; i < 4; i++) {
int newX = x + dir[i][0];
int newY = y + dir[i][1];
if (in(newX, newY) && maze[newX][newY] == '#' &&!vis[newX][newY]) {
dfs(newX, newY);
}
}
}
int main() {
freopen("cake.in","r",stdin);
freopen("cake.out","w",stdout);
cin>>n>>m;
for(int i=0;i>maze[i];
}
for(int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (maze[i][j] == '#' &&!vis[i][j]) {
cnt = 0;
dfs(i, j);
ans = max(ans, cnt);
}
}
}
cout << ans << endl;
return 0;
}