#include <bits/stdc++.h> 
 
using namespace std;  
 
typedef long long ll;  
typedef pair<int, int> ii;  
 
const int INF = 1e9;  
const ll LINF = 1e18;  
 
template<typename T>
void minimize(T& a, const T& b) {
	if (b < a) a = b; 
}
 
const int N = 2e4 + 5; 
 
int n, k;
int mask[N]; 
 
int hamming(int a, int b) {
	return __builtin_popcount(a ^ b);  
}
 
int main() {
	ios::sync_with_stdio(false); 
	cin.tie(nullptr); 	
	cin >> n >> k;  
	for (int i = 0; i < n; i++) {
		string s; cin >> s; 
		for (int j = 0; j < k; j++) {
			mask[i] |= (1 << j) * (s[j] - '0'); 
		}
	}
 
	int ans = INF;  
	for (int i = 0; i + 1 < n; i++) {
		for (int j = i + 1; j < n; j++) {
			minimize(ans, hamming(mask[i], mask[j])); 
		}
	}
 
	cout << ans << '\n'; 
}

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