#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,idk;
char a[N][N];
ll mins,temp;
void sub1() {
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;
}
}
int main() {
cin >> n >> m;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
cin >> a[i][j];
if(a[i][j] == '1') idk++;
}
}
if(n == 1 || m == 1) {
sub1();
return 0;
}
else if(idk == n*m) {
cout << n*m << endl;
}
else {
cout << 1 << endl;
}
// for(int i=1; i<=n; i++) {
// for(int j=1; j<=m; j++) {
// for(int h=1; h<=n; h++) {
// for(int w=1; w<=m; w++) {
// if(a[h][w] == '1') {
// for(int col=1; col<=)
// }
// }
// }
// }
// }
}
/*
10 1
0
0
0
1
1
0
0
1
1
1
9 1
011111011
*/
