#include <bits/stdc++.h>
using namespace std;
bool check(bool map[101][101],short x1,short y1,short x2,short y2){
	for (short i=x1;i<=x2;i++){
		for (short i1=y1;i1<=y2;i1++){
			if (map[i][i1]==0){
				return 0;
			}
		}
	}
	return 1;
}
bool find(short a,bool map[101][101],short n,short m){
	for (short i=0;i<=n-a;i++){
		for (short i1=0;i1<=m-a;i1++){
			if (check(map,i,i1,i+a-1,i1+a-1)==1){
				return 1;
			}
		}
	}
	return 0;
}
int main(){
	short n,m;
	bool map[101][101];
	cin >> n >> m;
	for (short i=0;i<n;i++){
		for (short i1=0;i1<m;i1++){
			cin >> map[i][i1];
		}
	}
	for (short i=max(n,m);i>1;i--){
		if (find(i,map,n,m)==1){
			cout << i;
			return 0;
		}
	}
	cout << 1;
	return 0;
}