#include <bits/stdc++.h>
using namespace std;
#define int ll
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<pi> vp;
typedef vector<pl> vpl;
const int maxn = 2505;
int a[maxn][maxn], n, m;
int prvi(int ind){
int cur = 0;
vi t;
for (int i = 0; i < m; ++i){
if (a[ind][i] == 1)
++cur;
else{
if (!cur) continue;
t.push_back(cur);
cur = 0;
}
}
if (cur)
t.push_back(cur);
if (t.empty())
return 0;
return *min_element(t.begin(), t.end());
}
int prvim(int ind){
int cur = 0;
vi t;
for (int i = 0; i < n; ++i){
if (a[i][ind] == 1)
++cur;
else{
if (!cur) continue;
t.push_back(cur);
cur = 0;
}
}
if (cur)
t.push_back(cur);
if (t.empty())
return 0;
return *min_element(t.begin(), t.end());
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cerr.tie(nullptr);
cin >> n >> m;
for (int i = 0; i < n; ++i){
string s;
cin >> s;
for (int j = 0; j < m; ++j)
a[i][j] = s[j]-'0';
}
if (n == 1)
return cout << prvi(0) << '\n', 0;
if (m == 1)
return cout << prvim(0) << '\n', 0;
int sol = prvi(0);
for (int i = 0; i < n; ++i){
int x = prvi(i);
if (!x) continue;
sol = min(sol, x);
}
int res = prvim(0);
for (int i = 0; i < m; ++i){
int x = prvim(i);
if (!x) continue;
res = min(res, x);
}
cout << max(sol, res) << '\n';
}
