#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using vvi = vector<vector<int>>;
int solve(vector<vector<int>>& b) {
	int N = b.size(), rowSum = 0, colSum = 0, rowSwap = 0, colSwap = 0;
	for (int i = 0; i < N; ++i) {
		for (int j = 0; j < N; ++j) {
			if (b[0][0]^b[i][0]^b[0][j]^b[i][j]) {
				return -1;
			}
		}
	}
	for (int i = 0; i < N; ++i) {
		rowSum += b[0][i];
		colSum += b[i][0];
		rowSwap += b[i][0] == i % 2;
		colSwap += b[0][i] == i % 2;
	}

	if (rowSum != N / 2 && rowSum != (N + 1) / 2) return -1;
	if (colSum != N / 2 && colSum != (N + 1) / 2) return -1;

	if (N % 2) {
		if (colSwap % 2) colSwap = N - colSwap;
		if (rowSwap % 2) rowSwap = N - rowSwap;
	}
	else {
		colSwap = min(N - colSwap, colSwap);
		rowSwap = min(N - rowSwap, rowSwap);
	}
	return (colSwap + rowSwap) / 2;
}

int main() {
	ll n, m;
	cin >> n >> m;
	vvi v(n, vector<int>(m));
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			cin >> v[i][j];
		}
	}
	cout << solve(v);
}