//
// Created by liasa on 15/11/2025.
//
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vll vector<ll>
#define loop(i, s, e) for (ll i = s; i < e; ++i)
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n, m;
cin >> n >> m;
vector<vll> grid(n, vll(m));
loop(i, 0, n) {
string s;
cin >> s;
loop(j, 0, m) { grid[i][j] = (s[j] - '0'); }
}
vll arr;
for (auto it : grid)
for (auto i : it)
arr.push_back(i);
ll ans = 1e18;
ll cnt = 0;
for (ll i = 0; i <arr.size(); ++i) {
if (arr[i] == 0) {
if (i != 0 && arr[i - 1] == 1)
ans = min(ans, cnt);
cnt = 0;
} else
cnt++;
}
cout << ans;
}
