#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;
#ifdef JASPER
#include "debug.h"
#else
#define debug(...) 166
#endif
signed main() {
cin.tie(0) -> sync_with_stdio(0);
int n, m;
cin >> n >> m;
vector <vector <int>> a(n + 5, vector <int> (m + 5, 0));
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
char x; cin >> x;
a[i][j] = x - '0';
}
}
//sub1: shortest consecutive 1ss
if (n == 1 || m == 1) {
if (n == 1) {
int ans = 1e9;
for (int i = 1; i <= m; ++i) {
if (a[1][i] == 0) continue;
int cur = 0;
while (i <= m && a[1][i]) {
++cur;
++i;
}
ans = min(ans, cur);
}
cout << ans << "\n";
}
if (m == 1) {
int ans = 1e9;
for (int i = 1; i <= n; ++i) {
if (a[i][1] == 0) continue;
int cur = 0;
while (i <= n && a[i][1]) {
++cur;
++i;
}
ans = min(ans, cur);
}
cout << ans << "\n";
}
}
}
