#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
const ll N = 2600;
ll n,m;
char a[N][N];
ll mins,temp;
int main() {
cin >> n >> m;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
cin >> a[i][j];
}
}
if(n == 1) {
mins = 1e9;
if(a[1][1] == '1') temp++;
for(int i=2; i<=m; i++) {
if(a[1][i] == a[1][i-1] && a[1][i] == '1') {
temp++;
}
else {
if(temp != 0)mins = min(mins,temp);
if(a[1][i] == '0') temp = 0;
else temp = 1;
}
}
if(temp != 0)mins = min(mins,temp);
cout << mins << endl;
}
else if(m == 1) {
mins = 1e9;
if(a[1][1] == '1') temp++;
for(int i=2; i<=n; i++) {
if(a[i][1] == a[i-1][1] && a[i][1] == '1') {
temp++;
}
else {
if(temp != 0)mins = min(mins,temp);
if(a[i][1] == '0') temp = 0;
else temp = 1;
}
}
if(temp != 0)mins = min(mins,temp);
cout << mins << endl;
}
}
/*
10 1
0
0
0
1
1
0
0
1
1
1
9 1
011111011
*/
